Draft

Advisory Board on Radiation and Worker Health

National Institute for Occupational Safety and Health

SC&A Review of Overall NIOSH Response to SC&A’s 

Supplemental Review of M&C Work Group Issues as of 

November 2023

Response Paper

Revision 0 PC-1 

Contract No. 75D30119C04183

Prepared by

Joe Fitzgerald, MS, MPH

SC&A, Inc.

2200 Wilson Blvd., Suite 300

Arlington, VA 22201-3324

November 22, 2023 

DISCLAIMER

This is a working document provided by the Centers for Disease Control and Prevention (CDC) 

technical support contractor, SC&A for use in discussions with the National Institute for 

Occupational Safety and Health (NIOSH) and the Advisory Board on Radiation and Worker 

Health (ABRWH), including its Working Groups or Subcommittees. Documents produced by 

SC&A, such as memorandum, white paper, draft or working documents are not final NIOSH or 

ABRWH products or positions, unless specifically marked as such. This document prepared by 

SC&A represents its preliminary evaluation on technical issues.

NOTICE: This document has been reviewed to identify and redact any information that is 

protected by the Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 2 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Table of Contents

Abbreviations and Acronyms........................................................................................... 4

1 Executive Summary.................................................................................................. 5

2 Introduction............................................................................................................... 9

3 Effects of Coagulant on Source Term....................................................................... 9

3.1 SC&A comment: Atomic Weapons Employer (AWE)-related coagulants in 

drain lines ................................................................................................................. 9

3.2 SC&A comment: Coagulant concentrations and maintenance workers ........ 10

4 Aerosolization of Drain Line Contamination (1,000,000 dpm/100 cm2) .................. 13

4.1 SC&A comment: Cleaning/cutting drain lines................................................ 13

4.2 SC&A comment: Bridgeport Brass hazard assessment ................................ 14

4.3 SC&A comment: Bridgeport Brass hazard assessment (pipe cutting) .......... 15

4.4 SC&A comment: Systemic or isolated drain line/pipe scale 

(1,000,000 dpm/100 cm2) ....................................................................................... 16

4.5 SC&A comment: Systemic or isolated drain line/pipe scale (additional survey 

evidence)................................................................................................................ 17

4.6 SC&A comment: Bounding exposure pathway.............................................. 22

5 Work in Confined Spaces ....................................................................................... 24

5.1 SC&A comment: Routine drain line repair in pits or trenches (6-month 

occupancy) ............................................................................................................. 24

5.2 SC&A comment: Confined spaces standard ................................................. 25

5.3 SC&A comment: Confined spaces and work not associated with drain line 

cleaning .................................................................................................................. 27

5.4 SC&A/Work Group comment: Applying Mound surrogate data to dust 

loading factor.......................................................................................................... 29

6 Additional Intrusive Activity Information for Table 1, Comparison of AWE Sites..... 31

6.1 NIOSH summary of SC&A table 1 and response (table 2 of NIOSH, 2023b) 31

7 M&C Work Group Concerns................................................................................... 33

7.1 Work Group concern: Data applicability ........................................................ 33

7.2 Work Group concern: Worker protection....................................................... 38

7.3 Work Group concern: Claimant-favorable assumptions ................................ 39

7.4 Work Group concern: AWE equipment ......................................................... 40

7.5 Work Group concern: Burial area.................................................................. 42

7.6 Work Group concern: Confined spaces and applying Mound surrogate data43

8 Other Issues of Significance................................................................................... 43
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 3 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

8.1 Application of extreme conservatism............................................................. 43

8.2 Conservatism of 95th percentile soil contamination value............................. 45

9 Conclusion.............................................................................................................. 46

10 References .......................................................................................................... 48
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 4 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Abbreviations and Acronyms

ABRWH, Board Advisory Board on Radiation and Worker Health 

AWE Atomic Weapons Employer 

AWWA American Water Works Association

CDC Centers for Disease Control and Prevention

CED committed effective dose

CI cast iron (pipe)

CFR Code of Federal Regulations 

cm centimeter

cpm counts per minute

D&D decontamination and decommissioning 

DCAS Division of Compensation Analysis and Support 

DOE U.S. Department of Energy 

dpm/100 cm2

 disintegrations per minute per 100 square centimeters

ER evaluation report 

g/m3 grams per cubic meter

HFIR High Flux Isotope Reactor 

HHS U.S. Department of Health and Human Services 

IAEA International Atomic Energy Agency 

M&C Metals and Controls Corporation 

μg/m3 micrograms per cubic meter

MRWA Minnesota Rural Water Association

NIOSH National Institute for Occupational Safety and Health

NRC U.S. Nuclear Regulatory Commission

ORAU Oak Ridge Associated Universities

ORAUT Oak Ridge Associated Universities Team

OSHA Occupational Safety and Health Administration

pCi/g picocuries per gram

PVC polyvinyl chloride

R&M repair and maintenance

SEC Special Exposure Cohort 

SRDB Site Research Database

TBD technical basis document 

TI Texas Instruments, Incorporated

U uranium 

VC vitreous clay (pipe) 

WG work group 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 5 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

1 Executive Summary

Special Exposure Cohort (SEC) Petition SEC-00236 for the Metals and Controls Corporation 

(M&C) in Attleboro, Massachusetts, was received on September 1, 2016, and qualified on 

November 14, 2016. The petition class evaluated by the National Institute for Occupational 

Safety and Health (NIOSH) was defined as:

All atomic weapons employees who worked as facilities construction and 

maintenance workers, including lubricators/oilers, industrial pipefitters, 

engineering technicians (mechanical, electrical, structural), maintenance 

supervisors, electricians, plumbers, millwrights, carpenters, instrumentation

technicians, chemical handlers, waste treatment operators, and all production 

workers, including machine operators/helpers and repair & maintenance 

(commonly called R&M) workers, who worked in Buildings 4, 5, 10 interior 

areas, and Buildings 5, 10, 11, 12, 17 exterior areas at Metals and Controls Corp. 

in Attleboro, Massachusetts, from January 1, 1968 through March 21, 1997. 

[NIOSH, 2017a, p. 3] 

SC&A’s review commenced in 2017, focusing on NIOSH’s evaluation report (ER) for M&C.

The original exposure potential was predicated on the more passive scenarios available in 

ORAUT-OTIB-0070, revision 01 (ORAUT, 2012; “OTIB-0070”), and Battelle-TBD-6000, 

revision 1 (NIOSH, 2011; “TBD-6000”), uranium process models for Atomic Weapons 

Employers (AWEs). NIOSH has since added six bounding exposure models to address workeridentified intrusive activities during the residual period. NIOSH and SC&A reached tacit 

agreement on these bounding models, but the M&C Work Group (WG) did not concur and in 

2021 requested further SC&A review. SC&A issued “Supplemental Review of M&C Work 

Group Issues” in August 2022 (SC&A, 2022), with a NIOSH response in January 2023 (NIOSH, 

2023a) and an SC&A response in April 2023 (SC&A, 2023). NIOSH issued a response to 

SC&A’s April 2023 paper on August 22, 2023 (NIOSH, 2023b), including an updated table 

comparing M&C with other AWEs for intrusive activities.

SC&A reviewed this most recent NIOSH response paper in the context of NIOSH’s overall 

response and reached the following specific conclusions about its key responses to SC&A and 

WG concerns, which are addressed in more detail in this paper. 

Effects of coagulant on source term. The issue is whether the routine discharge of a coagulant

oil, used as a lubricant for wiring operations in Building 10, into the drainage system over the 

duration of activities in that building may have led to consolidation and concentration of 

uranium- and thorium-contaminated sediments present in excess of the upper bound source term 

defined by NIOSH from the later 1995 pre-decontamination and decommissioning (D&D) 

characterization surveys. Given the unknown identity and properties of this coagulant oil, it is 

uncertain what the degree of consolidation and concentration of these suspended sediments 

would have been. Likewise, the rate and form of deposition for the consolidated sediment 

deposited inside the drain pipes is unknown. Notably, the resulting clogs containing these 

sediments are what M&C maintenance workers were exposed to in cutting and cleaning out these 

pipes. In its response, NIOSH (2023b) has provided no resolution to this issue. The presence of 

coagulant oils within the M&C drainage system in Building 10, the regular discharge of which 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 6 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

the workers attributed the clogging of drain pipes, may have led to increased concentrations for 

uranium- and thorium-contaminated sediments during the pre-1995 residual period, for which 

upper bound estimates may not be feasible. SC&A concludes that this question constitutes an 

SEC issue that pertains to the sufficient accuracy of the M&C Inside Subsurface source term for 

the WG to consider. 

Aerosolization of drain line interior surface contamination. The issue is whether NIOSH has 

adequately addressed contaminated scale (in addition to drain pipe sediment) in its inside 

subsurface exposure model to bound intakes by M&C maintenance workers during the residual 

period. While activity levels for interior pipe surface contamination were found to be “as high as 

1,000,000 dpm/100 cm2” in a pre-D&D survey (NIOSH, 2021, p. 7), only drainpipe sediment 

contaminant levels have heretofore been addressed as a source term by NIOSH’s exposure 

model. With only that single elevated measurement cited, supplemented by a few spot samplings 

of scale in drain pipes, it is not known whether this activity level can represent the highest 

measurement of scale similar to the 53,000 picocuries per gram (pCi/g) Priority 1 drain pipe 

sediment measurement from the 1995 sediment survey, which was among the numerous and 

distributed results from which the 95th percentile inside subsurface bounding value of 

6,887 pCi/g was derived. This is compounded by the difficulty and uncertainty of translating 

direct radiation measurements to interior pipe surface contamination levels, as confirmed by 

Weston in its pre-D&D surveys (refer to section 4.5).

NIOSH’s recent use of U.S. Department of Energy (DOE) parameters and methods from the 

Bridgeport Brass AWE hazard assessment (DOE, 1996) to calculate a corresponding worker 

dose based on the million disintegrations per minute per 100 square centimeters (dpm/100 cm2

) 

survey result raises uncertainties surrounding the lack of M&C-specific data and information to 

support that calculation. The uncertainty surrounding the lack of systematic and representative 

M&C survey measurements for scale is compounded by (1) uncertainties surrounding the nature, 

composition, and formation of scale in the presence of an oil-based coagulant and 

(2) uncertainties involving the exposure pathway for maintenance workers in terms of inhalation 

of fumes and volatized material due to power or torch cutting and cleaning of drain pipes. SC&A 

finds that NIOSH’s inside subsurface exposure model does not address this source term 

adequately, and, therefore, the proposed bounding dose may not be sufficiently accurate. SC&A 

concludes that this question constitutes an SEC issue for the WG to consider. 

Work in confined spaces. SC&A’s original finding (SC&A, 2022, finding 2) was that NIOSH’s 

proposed application of Mound project data for deriving the M&C dust loading factor does not 

satisfy the Advisory Board on Radiation and Worker Health (ABRWH, “Board”) surrogate data 

policy for site and process similarity given disparities between the sites for confined space 

conditions. The use of the Mound-based dust loading factor as one of the “three legs of the 

stool”1

1 The other two are source term and occupancy/time. 

(ABRWH, 2023b, slide 15) for NIOSH’s bounding intake approach for M&C may, 

therefore, not be sufficiently accurate for that purpose. However, with (1) SC&A’s

acknowledgment that this is essentially a technical basis document (TBD) issue and (2) NIOSH’s 

acceptance that it will need to review “recent suggestions to upgrade its dust loading models, 

including enhancement factors and confined spaces, and will consider incorporating methods 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 7 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

suggested by SC&A in their supplemental review” (NIOSH, 2023b, p. 24), SC&A recommends 

that the issue of the dust loading factor for M&C be pended for resolution by the WG awaiting 

the results of that review.

Additional intrusive activity information for table 1 comparison of AWE sites. SC&A finds 

that some of the residual period activities noted by NIOSH in its new table 2 for other AWEs 

bears some resemblance to those at M&C. However, by its action to derive six exposure models 

for M&C, NIOSH itself acknowledges that these intrusive maintenance activities were 

sufficiently distinct from the more passive resuspension scenarios in OTIB-0070 and TBD-6000, 

and differed from experience at these other AWEs, to warrant special treatment from an 

exposure bounding standpoint. 

Data applicability (Work Group concern). A judgment on the question of whether there is 

sufficient similarity of conditions and processes between the D&D era, during which the 1995 

characterization sampling was conducted, and the preceding M&C residual period maintenance 

activities resides with the Board, as it did for Linde Ceramics on a similar question between 

Linde’s D&D and renovation periods. But it is clear that there are uncertainties related to source 

terms and exposure pathways for the M&C residual period, in addition to different conditions 

and processes, that may not be adequately addressed by NIOSH’s current inside subsurface 

bounding model that is founded on pre-D&D sampling.

Application of “extreme conservatism.” In its most recent response, NIOSH (2023b, p. 32) 

claims that “SC&A and the Work Group are misinterpreting NIOSH’s use of the phrase ‘extreme 

conservatism’ to mean implausibly high” and counters that it is “using conservative assumptions 

that are appropriate for a bounding scenario.” SC&A has cited NIOSH’s defined application and 

scope of “extreme conservatism” precisely as given and in the context that it was given. Given 

the breadth and depth of unknowns and uncertainties for M&C’s residual period inherent in this 

bounding approach, it will be incumbent on the Board to gauge whether the application of 

extreme conservatism—and the assumptions inherent in such an approach—represents a 

plausible means to define an upper bound for past exposures of M&C maintenance workers 

during the 27 years in question. Likewise, if NIOSH’s bounding model cannot account for 

M&C’s “intrusive activities, high exposure conditions, uncertain facility activities, or unknown 

contamination sources” (NIOSH, 2023a, p. 17) without resorting to extreme conservatism, 

sufficient accuracy becomes a concern.

Conservatism of 95th percentile soil contamination value.

2

2 This issue was raised as observation 2 in SC&A’s (2022) supplemental review and addressed in subsequent 

NIOSH and SC&A responses but was not addressed in NIOSH’s August 2023 response paper. 

 In its 2021 response to WG 

questions, NIOSH proceeded to “make the case that M&C’s area monitoring assures that the 

95th percentile soil-contamination value is conservative based on routine surveys of Building 10 

during the first 14 years of the residual period (1968-1981)” (NIOSH, 2021, pp. 7–8; emphasis 

added). In response to SC&A’s (2022) supplemental review observation 2, NIOSH noted that it 

“was not using the M&C Safety and Health manual, NRC inspection results, operator training, 

and other programmatic considerations to justify using the 95th percentile” (NIOSH, 2023a, 

p. 23). In its April 2023 response, SC&A emphasized that “whether using these program 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 8 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

documents to justify, or to demonstrate, corroborate, illustrate, or show that such monitoring 

procedures and oversight ‘assures’ that the 95th percentile soil contamination value is 

conservative is a distinction with little difference” (SC&A, 2023, p. 12). In that response, SC&A 

reaffirmed that it stands by its observation that the program references NIOSH cites “do not 

necessarily substantiate the conservatism of the 95th percentile soil contamination value being 

applied” (SC&A, 2023, p. 12).

Overall conclusion. SC&A concludes that NIOSH has a pathway to address the confined space 

issue, which is acknowledged as a TBD concern, and for which options for revised resuspension 

factors and a derived dust loading factor have been identified. However, uncertainties remain for 

source terms related to in-pipe contaminated sediments (due to the presence of coagulants), inpipe interior surface contamination (scale), and residual contamination in repurposed AWE-era 

machinery and equipment, respectively, which are not accounted for in the proposed inside 

subsurface bounding model. Concentrations of in-pipe sediments and scale may have been 

higher during the 27 years of M&C maintenance activities involving pipe cutting and cleanout 

that preceded the 1995 survey upon which NIOSH’s inside subsurface bounding value is based. 

This is the basis for SC&A’s finding 1 of its supplemental review. As acknowledged by NIOSH, 

the extreme conservatism of this bounding value is meant to address the inherent unknowns and 

uncertainties in this back-application of source term, but the Board may not consider such an 

approach to be a plausible means to do so. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 9 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

2 Introduction

The remainder of this paper responds to NIOSH’s corresponding responses to SC&A’s 

April 2023 review. It follows the same issue organization and format as NIOSH’s most recent 

August 22, 2023, response paper (NIOSH, 2023b). For each issue, NIOSH (2023b) first quoted 

SC&A’s comments, then gave NIOSH’s response. In this paper, each issue section begins with 

the relevant SC&A (2023) and/or M&C WG comments, followed by either a quote from 

NIOSH’s August 22, 2023, response or (where necessary for brevity) a summary of that 

response, and finally SC&A’s response. In a few cases where NIOSH responded more than once 

to the same issue, SC&A’s summary reflects both responses.

3 Effects of Coagulant on Source Term

3.1 SC&A comment: Atomic Weapons Employer (AWE)-related coagulants in 

drain lines

The release of nonradioactive coagulant oil to drain lines was done separately 

from any HFIR operational radioactive releases and may have had a collateral 

influence on how AWE-related uranium and thorium contamination already in the 

piping would have concentrated over the years following those original 

discharges. In fact, in its response, NIOSH supports this interpretation by making 

the case that “wire operations during the residual period did not process 

radioactive materials; therefore, most material rinsed into the drains was nonradioactive except for residual contamination that remained in cracks and 

crevices” (NIOSH [2023a], p. 12). SC&A agrees with NIOSH that the wiring 

operations did not contribute radioactive materials to the drain lines. It was the 

coagulant oil itself that may have consolidated the uranium and thorium already 

entrained in the pipes (“cracks and crevices”) that would have impacted the 

covered AWE material from prior years (the resulting sediment would not have 

been distinguishable between AWE and HFIR residual contamination). [SC&A, 

2023, pp. 6–7] 

3.1.1 NIOSH response: AWE-related coagulants in drain lines

There appears to be a misinterpretation of the following NIOSH statement: 

More specifically, wire operations during the residual period did not 

process radioactive materials; therefore, most material rinsed into the 

drains was non-radioactive except for residual contamination that 

remained in cracks and crevices, as shown in the following figures.

[NIOSH [2023a], PDF p. 17] 

Although it is still possible that there were cracks and crevices within the drain 

lines as SC&A describes, NIOSH refers to the low-level contamination that 

remained in the cracks and crevices under the wire machines, as shown on the 

subsequent pages in Figures 1 and 2 of NIOSH [[2023a], PDF pp. 18–19]. 

[NIOSH, 2023b, p. 3] 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 10 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

3.1.2 SC&A response

SC&A was responding to NIOSH’s contention that “the release of coagulant oil and production 

materials carried with it did not introduce higher concentrations of covered uranium and thorium 

from AWE operations (1952–1967) to the subsurface” (NIOSH, 2023a, p. 12), but accepts 

NIOSH’s clarification that it was referring to “cracks and crevices” underneath the wiring 

machines containing residual contamination (NIOSH, 2023b, p. 3). However, this distinction 

does not change SC&A’s finding that coagulant oils could have consolidated and concentrated 

existing residual contamination in the drainage system, including that in pipe cracks and 

crevices, thus leading to potentially higher radiological source terms over the early M&C 

residual years preceding the 1995 pre-D&D characterizations.

3.2 SC&A comment: Coagulant concentrations and maintenance workers

The AWE sediment was clearly present within the system following the cessation 

of AWE operations; any later introduction of oil-based coagulant solutions within 

that system may have collected and concentrated the uranium and thorium already 

present in that system and led to higher sedimentation to which M&C 

maintenance workers would have been exposed. This concern represents a new 

issue that has not been addressed. [SC&A, 2023, p. 7] 

3.2.1 NIOSH response: Coagulant concentrations and maintenance workers

NIOSH cites an interview with an M&C maintenance supervisor regarding the wire drawing 

operation and the “green lube” coagulant oil used in that operation (NIOSH, 2023b, p. 4). 

NIOSH observes that “although these excerpts do not directly address SC&A’s concern, they do 

reveal that this maintenance supervisor may know additional details worth pursuing” (NIOSH, 

2023b, p. 4). NIOSH indicates that when revisions are made to the M&C TBD, NIOSH will

(NIOSH, 2023b, p. 4): 

• Identify the locations of wire machines in Building 10 and overlay their 

locations above the drain lines to indicate their distance from Priority 1 

drain lines.

• Mark-up the drain lines with flow paths to determine which lines were 

downstream of the coagulant sources (i.e., wire machines).

NIOSH (2023b, p. 5) also notes several other considerations that it believes are relevant to the 

issue: 

• Weston could have noted and collected coagulant when they characterized the 

drain lines, as described in the following. “After pipes were opened, a sample 

of the sediment or other residue in the pipe was collected and submitted for 

isotopic and/or total uranium analyses” [Weston, 1996b, PDF p. 11]. For 

example, the clay pipe with the highest interior surface contamination 

(1,000,000 disintegrations per minute [dpm]/100 cm2

) “did not contain a 

visible accumulation of residue” [Weston 1996b, PDF p. 11]. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 11 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

• The airborne hazard associated with cleaning clogged pipes was minimal 

because the material was wet, and the presence of coagulants functioned as 

glue, effectively locking/fixing contamination in place along the pipe’s 

interior surfaces. These conditions significantly reduced the resuspension and 

respirability of the source term, eliminating the coagulant concern from 

consideration as a bounding internal dose scenario for NIOSH to incorporate. 

The fixed contamination could be an external contributor that NIOSH’s 

external dose model will address. NIOSH requests SC&A to supply a 

technical justification showing that a coagulant can function as both a 

substance that is sticky enough to clog drains and allow resuspension of 

respirable particles.

• NIOSH’s experience with surface contamination indicates it would either 

travel through and exit the system or become fixed such that an aggressive 

decontamination technique would be required to move it through the system. 

NIOSH performed a literature search to confirm SC&A’s assertion and 

studied vegetable/mineral oils to determine their physical properties (e.g., pH) 

to see if they possessed solvent properties sufficient to mobilize a fixed 

contaminant and accumulate it downstream. NIOSH did not find any 

supporting information in the technical literature. If SC&A is aware of such 

information, NIOSH will consider it.

Finally, NIOSH concludes that it has “determined that it can describe plausibly, and bound 

exposures associated with unclogging pipes while accounting for the effects of introducing a 

nonradioactive coagulant to the drain line source term” (NIOSH, 2023b, p. 5). 

3.2.2 SC&A response

NIOSH’s response regarding the regular presence of coagulant oils within M&C drain lines does 

not change SC&A’s original conclusion about the source term implications of this unknown 

substance for existing uranium- and thorium-contaminated sediments:

SC&A agrees with NIOSH that the wiring operations did not contribute 

radioactive materials to the drain lines. It was the coagulant oil itself that may 

have consolidated the uranium and thorium already entrained in the pipes . . . that 

would have impacted the covered AWE material from prior years (the resulting 

sediment would not have been distinguishable between AWE and HFIR residual 

contamination). The AWE sediment was clearly present within the system 

following the cessation of AWE operations; any later introduction of oil-based 

coagulant solutions within that system may have collected and concentrated the 

uranium and thorium already present in that system and led to higher 

sedimentation to which M&C maintenance workers would have been exposed. 

[SC&A, 2023, p. 7] 

Whether or not Weston would have identified and collected coagulant during their 

characterization work does not comport with the physical and chemical properties of coagulants 

and how they actually function. Coagulants and the coagulant mechanism can be explained as 

follows (CDC, 2022):
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 12 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Coagulation is often the first step in water treatment. During coagulation, 

chemicals with a positive charge are added to the water. The positive charge 

neutralizes the negative charge of dirt and other dissolved particles in the water. 

When this occurs, the particles bind with the chemicals to form slightly larger 

particles. Common chemicals used in this step include specific types of salts, 

aluminum, or iron. 

In other words, coagulants are substances that can neutralize the normally repulsive electrical 

charge of particles in a suspended solution such that the particles will begin to consolidate, or 

cling together, forming floc that settle out in the form of a binding sediment or sludge-like 

substrate that in wastewater treatment (for example) enables them to be more readily removed

(MRWA, 2020; AWWA, 2011). Once they have done this job, the coagulants themselves have 

ceased to exist in their original form. Therefore, there are no coagulants, per se, that could have 

been identified and collected by Weston, only the resulting consolidated and concentrated 

particles or sediments that were the result of the coagulant effect that had come out of suspension 

and settled out within the drainage pipe. 

In this context, it is not accurate to describe the coagulants as “sticky” or functioning as a “glue” 

for the drainpipe sediments (NIOSH, 2023b, p. 5). As already described, the properties of 

coagulants are to neutralize naturally repellant electrical charges of particles or sediments. There 

is considerable scientific, industry, and government literature available regarding this 

phenomenon and its long and wide application, particularly for drinking and waste water 

treatment. The following references from the published scientific literature, government fact 

sheets, and industry trade journals are particularly relevant. 

References for general properties, functions, and experience with coagulants in water treatment:

• Centers for Disease Control and Prevention (CDC, 2022), “Water Treatment” 

• Campbell (2022), “What is Coagulation for Water Treatment?” 

• Safe Drinking Water Foundation (n.d.), “Conventional Water Treatment: Coagulation 

and Treatment” 

• American Water Works Association (AWWA). (2011). AWWA Manual M37, 

Operational Control of Coagulation and Filtration Processes, third edition

• Minnesota Rural Water Association (MRWA). (2020). Minnesota Water Works 

Operations Manual, Chapter 12, “Coagulation and Flocculation” 

While the identity and properties of the oil-based coagulant introduced during the M&C residual 

period are unknown, there is literature on the use of natural or plant-based coagulants that may 

be relevant: 

• Vijayaraghavan, Sivakumar, and Vimal Kumar (2011), “Application of Plant Based 

Coagulants for Waste Water Treatment” 

• Saleem & Bachmann (2019), “A Contemporary Review on Plant-Based Coagulants for 

Applications in Water Treatment” 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 13 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

• Alazaiza et al. (2022), “Application of Natural Coagulants for Pharmaceutical Removal

from Water and Wastewater: A Review”

Regarding NIOSH’s comment on the mobility of pipe contamination, SC&A has already 

clarified that a key impact of regularly introduced coagulant oil would be to consolidate (bind) 

and concentrate whatever contaminated sediment, presumably waterborne suspended 

particulates, was already present within the M&C drainage system, leading to potentially 

increased concentrations of contaminant deposits within the pipes. Whether the coagulant 

involved had “solvent” properties to “mobilize a fixed contaminant” (NIOSH, 2023b, p. 5) 

would be speculative at this point, without knowing the specific coagulant employed (beyond 

what was remembered as “green lube” (NIOSH, 2023b, p. 4)), its chemical and physical 

properties, the chemical and physical properties of whatever fixed contamination existed within 

the M&C drainage pipes, and the properties of the water solution inside the drain during 

discharges (e.g., pH, volume, speed of passage). However, it is clear that during the M&C 

residual period, the drainage pipes would have contained both in-solution suspended sediments 

and fixed sediment contamination of varying degrees, for which the regular introduction of an 

oil-based coagulant during Building 10 operations was known by M&C workers to consolidate 

or bind in-pipe sediments such that drain pipes became plugged, requiring cleanout. Again, the 

chemical and physical form of the actual consolidated sediment making up these clogs is not 

known beyond the uranium concentrations determined. 

4 Aerosolization of Drain Line Contamination (1,000,000 dpm/100 cm2) 

4.1 SC&A comment: Cleaning/cutting drain lines

Another historical aspect of M&C drain lines is the accumulation of contaminant 

scale that has plated out inside the piping. This scaling was found in at least one 

instance at M&C to exceed[3

3 This reference was incorrectly cited by SC&A as “to exceed” rather than “as high as” 1,000,000 dpm/100 cm2

. 

]

 1,000,000 dpm/100 cm2 in a 4-inch mainline drain 

that was being cut and removed (NIOSH, [2021], p. 7). While such pipe scale has 

been identified at other AWE sites, M&C maintenance workers frequently cut, 

repaired, replaced, and cleaned out such piping during the residual years using 

power tools such as saws, drills, grinders, and powered snakes, as well as cutting 

torches. [SC&A, 2022, p. 21] 

4.1.1 NIOSH response: Cleaning/cutting drain lines

SC&A begins the paragraph above discussing drain lines, which NIOSH and 

SC&A agree represent the most significant source term. 

Regarding the following SC&A excerpt from above: 

M&C maintenance workers frequently cut, repaired, replaced, and 

cleaned out such piping during the residual years using power tools such 

as saws, drills, grinders, and powered snakes, as well as cutting torches. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 14 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

The drain lines of concern were either cast iron or clay and would have been cut 

with a snap-cutter or saw and not routinely cut with torches. There were other 

services that traversed the subsurface (e.g., airlines, recirculation piping); 

however, NIOSH does not consider work performed in the subsurface at a 

distance (>5 ft) from the drain lines to represent the bounding scenario. 

[NIOSH, 2023b, p. 6] 

4.1.2 SC&A response

As NIOSH observes, SC&A and NIOSH agree that the most significant source terms are those 

related to cutting and cleaning of drain lines. As cited by NIOSH in its response, SC&A notes 

that a wide array of intrusive activities, many involving power tools, were used to cut, clean out, 

and repair these pipes, including saws, drills, grinders, powered snakes, and cutting torches. The 

specific tools employed would have depended upon the type of pipe (e.g., cast iron versus clay), 

the size and nature of the clog, and the size and condition of the pipe. 

SC&A agrees that while snapcutters and saws would have been more routine than cutting 

torches, the volatizing and suspension of fine particles or fumes of contaminated scale (or other 

interior pipe surface contamination) during all of these mechanized activities is the issue—one 

that was highlighted by DOE in its hazard assessment example involving pipe cutting using a 

cutting torch. All of this work would have been performed within the 5-feet criterion noted by 

NIOSH and would have likewise been often performed in a confined space atmosphere that 

would have had the potential for concentrating generated fumes and particulates in the breathing 

zone of the worker handling this equipment.

4.2 SC&A comment: Bridgeport Brass hazard assessment

As noted by DOE in its hazard assessment of the Bridgeport Brass AWE, “the 

residual uranium could eventually be released . . . through intrusive work 

activities such as pipe cutting and removal” (DOE, 1996, PDF p. 11), and that “it 

is possible that under certain conditions (such as cutting through a steel pipe with 

a cutting torch) surface activity attached to the steel could be released with the 

steel particles” (DOE, 1996, PDF p. 48). [SC&A, 2022, PDF p. 21] 

4.2.1 NIOSH response: Bridgeport Brass hazard assessment (torch cutting)

The excerpt above shows why the reference provided by SC&A is concerned with 

the torch cutting of drain lines, and since M&C’s drain lines were not steel, 

NIOSH did not select torch cutting of drain lines as a bounding scenario. 

NIOSH reviewed the U.S. Department of Energy (DOE) Bridgeport Brass AWE 

Hazard Assessment [DOE 1996] referenced by SC&A to determine the types of 

pipes that were cut with torches and found the following:

Many of the drain lines at the GM site are constructed of carbon steel. It 

is unlikely that contamination could penetrate uniformly as deep as 1 cm 

into carbon steel (or even clay tile pipes). [DOE 1996, PDF p. 47] 

[NIOSH, 2023b, pp. 6–7] 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 15 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

4.2.2 SC&A response

As noted in the preceding response, SC&A identified a range of intrusive, mechanized processes 

by which drain pipes were cut, cleaned out, and repaired, of which torch cutting was identified as 

one such means. While the Bridgeport Brass AWE hazard assessment focuses on the cutting of 

steel pipes, torch cutting was among several means by which cast iron (CI) pipes and vitreous 

clay (VC) pipes were cut at M&C by maintenance workers. Any of the mechanized cutting and 

repair procedures may have volatized and suspended any contaminated scale that would have 

been present on the inside of the VC or CI drain pipes being worked on. The Bridgeport Brass 

AWE cautionary note on torch cutting of pipes by DOE was provided to highlight this concern 

for a scenario that would have likely provided the upper range of airborne contamination given 

the added heat and energy involved. However, electric drills, grinders, and powered snakes may 

have likewise served to release any contaminated scale present on the inside of the piping.

As for the penetration of contamination into either CI or VC pipes at M&C, there are no data to 

support the degree to which surface contamination on the interior of such pipes would have 

adhered to, penetrated, or deposited within the M&C drainage system. The only data are from the 

D&D characterization surveys in terms of what was actually measured, in a very limited way, as 

surface contamination for pipe interiors.

4.3 SC&A comment: Bridgeport Brass hazard assessment (pipe cutting)

NIOSH fails to address the source of this concern: the U.S. Department of 

Energy’s (DOE’s) Bridgeport Brass AWE hazard assessment, where it was 

warned that pipe cutting involving internal radioactive contamination could lead 

to airborne releases that may involve worker exposure (DOE, 1996, PDF p. 48). 

[SC&A, 2023, p. 7] 

4.3.1 NIOSH response: Bridgeport Brass hazard assessment (pipe cutting)

“NIOSH reviewed the complete Bridgeport Brass Hazard Assessment [DOE 1996] referenced by

SC&A” (NIOSH, 2023b, p. 7) and detailed its findings, including source terms, exposure 

pathways, and a comparison with M&C regarding maximum source term and annual total 

effective dose.

4.3.2 SC&A response

The context of SC&A’s original comment was to point out the source of its concern regarding 

pipe cutting involving interior surface radioactive contamination, which was underscored in 

DOE’s hazard assessment for the Bridgeport Brass AWE. NIOSH has now acknowledged its 

review of this issue, as well as an overall assessment of that report. Regarding NIOSH’s 

comment that the “ratio of assigned dose to source term level using the Bridgeport Brass 

reference SC&A recommended compares favorably to that proposed for M&C” (NIOSH, 2023b, 

p. 8), SC&A did not recommend the Bridgeport Brass exposure modeling for direct application 

to M&C. It was cited to illustrate that in-pipe surface contamination can be a credible source 

term that also needs to be considered for M&C from an exposure pathway standpoint. The 

physical characteristics of the piping at Bridgewater Brass, the specific source term involved, 

and the thickness of in-pipe surface contamination (identified by DOE as the most significant 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 16 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

variable), make a direct comparison with M&C problematic given differences between the two 

sites and the uncertainties of these parameters for M&C.

4.4 SC&A comment: Systemic or isolated drain line/pipe scale 

(1,000,000 dpm/100 cm2) 

NIOSH contends that cutting of drain lines with contaminated scale exceeding 

1,000,000 disintegrations per minute per 100 square centimeters (dpm/100 cm2) 

would constitute “isolated hot spots,” not a systemic condition, and that in any 

case, it does not believe there is any evidence that even higher activity levels 

might have existed. [SC&A, 2023, p. 7] 

4.4.1 NIOSH response: Systemic or isolated drain line/pipe scale 

(1,000,000 dpm/100 cm2

) 

SC&A’s line of inquiry about pipe scale stems from a misinterpretation of one 

survey indicating a contamination level of 1,000,000 dpm/100 cm2 found in the 

Screen Print Room (Area 7). The following is from SC&A’s Supplemental 

Review of M&C Work Group Issues: 

Another historical aspect of M&C drain lines is the accumulation of 

contaminant scale that has plated out inside the piping. This scaling was 

found in at least one instance at M&C to exceed 1,000,000 dpm/100 cm2

in a 4-inch mainline drain that was being cut and removed (NIOSH, 

[2021], p. 7). [SC&A 2022, PDF p. 22] 

The Weston [1996b] drainage system characterization does not identify any scale 

found at the location SC&A references [PDF pp. 10–11]. As NIOSH previously 

noted, this drain line was clay; scale/rust is associated with cast iron drain lines. 

To further clarify, this pipe had contamination levels as high as 1,000,000 

dpm/100 cm2

 and was cut and removed by Weston decontamination and 

decommissioning (D&D) workers, not as part of M&C maintenance work. 

[NIOSH, 2023b, p. 8] 

4.4.2 SC&A response

To be precise, the one survey result cited by SC&A from NIOSH’s 2021 response paper is 

explained in an excerpt from that response paper, as follows (p. 7): 

During contaminated concrete removal at the north side of the Screen Print Room 

(Area 7), the initiation point of a 4-inch vitreous clay (VC) mainline was 

encountered. This line exhibited surface contamination levels (on the pipe 

interior) as high as 1,000,000 dpm/100 cm2

, although did not contain a visible 

accumulation of residue. Approximately 15 feet of line was removed until surface 

contamination levels within the pipe were reduced to background levels.

[emphasis added] 

NIOSH concludes that scale would only be associated with CI pipes but provides no evidence 

that this was the case at M&C (though specific scale survey results were reported by Weston for 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 17 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

a few CI pipes and rust may obviously also be present with CI pipes). The one million 

dpm/100 cm2 measurement was for the initiation point for a VC mainline. The VC lines accepted 

flows from floor drains, while CI lines accepted flows from the roof of Building 10 (Weston, 

1996b, PDF p. 7).4

4

 Workers indicated that there had been some “cross routing” between the systems over time (Weston 1996b, PDF 

p. 7), as corroborated by an interview with an M&C maintenance worker who noted that excess drain water with 

“green lube” in it had been apparently pumped into a roof drain and turned the pond green (ORAUT, 2017c, PDF 

pp. 12–13).

The 1,000,000 dpm/100 cm2 “surface contamination levels (on the pipe interior)” of the VC 

mainline pipe “did not contain a visible accumulation of residue,” as reported by the Weston 

survey (Weston, 1996b, PDF pp. 10–11), which correlates with scale readings taking in other 

locations (e.g., survey locations 2, 3, 4 and 5, cited by NIOSH and summarized in section 4.5). 

For example, for the scale readings in locations 4 and 5, the Weston survey reported that 

“sampling and visual observation confirmed that there was little to no accumulation of residue in 

these lines” (Weston 1996b, PDF p. 17). That Weston did not label this 1,000,000 dpm/100 cm2

surface contamination as scale is a distinction with little difference as it was found to be a high 

contamination level on the interior surface of this drain pipe with little visible accumulation of 

residue sediment associated with it. The apparent interchangeability of such terminology (scale 

versus interior surface contamination) is further borne out as noted by survey data for Areas 1 

and 4 (refer to SC&A’s response in section 4.5 of this paper). 

Whether the pipe in question was cut and removed by D&D workers versus M&C maintenance 

workers is beside the point. The presence of contaminated scale and similar in-pipe surface 

contamination (without associated residue) within the drainage pipe system at M&C during the 

residual period represents a potential source term for which limited sampling was performed 

during D&D characterization and for which uncertainties remain.

4.5 SC&A comment: Systemic or isolated drain line/pipe scale (additional survey 

evidence) 

NIOSH presents no evidence that this contaminated scale would not have been 

present elsewhere in the piping system, could have involved both metal and clay 

pipes, or that even higher activity levels may have been present elsewhere in the 

pipe network. [SC&A, 2023, p. 7] 

4.5.1 NIOSH response: Systemic or isolated drain line/pipe scale (additional survey 

evidence)

NIOSH notes that it “relies on the available source-term survey data because of the 

comprehensiveness exercised by Weston and Texas Instruments” (NIOSH, 2023b, p. 9) in its 

M&C assessments and surveys, and the methods employed during those assessments. It also 

notes that “in addition to the systematic sampling prescribed by NUREG/CR-5849, Weston 

collected biased samples at ‘cracks or other locations across the grid exhibiting elevated surface 

activity measurements’ [Weston 1995, PDF p. 6]” (NIOSH, 2023b, p. 9). In terms of “existing 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 18 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

scale data” (NIOSH, 2023b, p. 9) from sampling performed by Weston, NIOSH provided the 

following information in its April 2023 response paper.5

 

5 This is in addition to the 1,000,000 dpm/100 cm2 survey of the interior surface of a CI mainline pipe in Area 7, 

which NIOSH noted in the response discussed in section 4.4 of this paper was not labeled as scale by Weston.

Weston January 1996 drainage system characterization survey data (Weston, 1996b): 

Weston reported collecting scale samples at locations 2, 3, 4, and 5 [Weston 

1996b, PDF pp. 15, 17] that provide contamination data as high as 507.7 pCi/g 

[Weston 1996b, PDF p. 18]. In addition, NIOSH has the following information: 

• In the Caged Area (Areas 1 and 4 where the fuel rod was found), radiological 

surveys of this piping typically showed marginal surface contamination on the 

interiors of the pipes, typically ranging from less than 3000 dpm/100 cm2

[Weston 1996b, PDF p. 10]. 

• Locations 4 and 5 accessed lines that had previously supported assay 

laboratories associated with nuclear material manufacturing activities. 

Sampling and visual observation confirmed that these lines had little to no 

residue accumulation. Analytical data for both CI lines showed a total 

uranium concentration of approximately 500 pCi/g in the thin layer of scale 

[Weston 1996a, PDF p. 17]. 

[NIOSH, 2023b, p. 9] 

Weston October 1996 remediation of building interiors, Buildings 4, 5, and 10 survey data 

(Weston 1996a): 

• Areas 3 and 4 were identified as having scale and rust with a total uranium 

concentration of 1,864 pCi/g [Weston 1996a, PDF p. 174]. 

[NIOSH, 2023b, p. 9] 

Beyond the cited survey data, NIOSH indicates that it “can use Weston [1996b] Table 3, 

Building 10 Feed Drain Surveys [PDF p. 21], particularly the beta scintillator data as scale 

activity measurements” (NIOSH 2023b, p. 10). NIOSH also observed that “M&C also developed 

a method to calculate surface contamination levels on pipe interiors using the thickness of 

residue lining the pipes and the total uranium concentration in the residue” and that this method 

and source term data (as outlined in Weston, 1997a, PDF pp. 11, 13, 15) can support “drain 

calculations with conversions to surface activity where total surface contamination levels prior to 

decontamination ranged from 53,000 to 95,000 dpm/100 cm2

” (NIOSH, 2023b, p. 10). 

NIOSH concludes that: 

In summary, neither SC&A nor the M&C Work Group has provided any evidence 

explaining why these surveys are not a suitable basis for NIOSH’s bounding 

source term. This issue boils down to a demand that NIOSH prove a negative (i.e., 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 19 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

prove something did not exist). NIOSH has cited credible evidence to support its 

calculations. Assertions that there could have been other higher contamination 

levels—with no supporting evidence—rely on speculation. NIOSH’s model using 

the pre-D&D survey that included a fuel pin in the pipe is the highest plausible 

bounding scenario. NIOSH has not received any technical evidence contradicting 

the use of this survey in a bounding model. [NIOSH, 2023b, p. 10] 

4.5.2 SC&A response

The following is in response to the specific survey data highlighted by NIOSH pertaining to 

interior pipe scale.

NIOSH: “Weston reported collecting scale samples at locations 2, 3, 4, and 5 [Weston 1996b, 

PDF pp. 15, 17] that provide contamination data as high as 507.7 pCi/g [Weston 1996b, PDF 

p. 18]” (NIOSH, 2023b, p. 9). 

SC&A response: The scope of the cited sampling of scale is very limited for purposes of 

characterizing the range of activity levels within M&C drain pipes and what may represent the 

upper bound of that activity. Weston relied upon two primary programs: (1) sampling and 

analyses of in-pipe residue and (2) radiological measurements within the interiors of arterial and 

feed piping (Weston, 1996b, PDF p. 11). For the latter, a Ludlum Model 44-1 beta scintillator 

was used in 8 to 10 feed lines as a means to identify contaminated scale (Weston, 1996b, 

PDF p. 12). In terms of characterizing in-pipe surface contamination levels, Weston confirmed 

the difficulty of translating direct radiation measurements to interior pipe surface contamination 

levels: 

Correlation of direct radiation measurements to interior pipe surface 

contamination levels is hampered by irregular surfaces in the drain lines, the 

presence of larger blockages, varying geometries, the presence of radium and 

other naturally-occurring radioactive material (NORM), and the presence of 

moisture and liquid resulting from active facility discharges. [Weston, 1997a, 

PDF p. 11] 

These limitations would have also hampered the representative identification and 

characterization of scale in piping at M&C using direct radiological scanning.

As it stands, the Weston characterization survey of M&C in-pipe scale can only be attributed to 

two drain pipe measurements supporting one Building 10 operation (assay laboratories), as noted 

in the following review of NIOSH’s survey results. 

NIOSH: “In the Caged Area (Areas 1 and 4 where the fuel rod was found), radiological surveys 

of this piping typically showed marginal surface contamination on the interiors of the pipes, 

typically ranging from less than 3000 dpm/100 cm2 [Weston 1996b, PDF p. 10]” (NIOSH 2023b, 

p. 9). 

SC&A response: These measurements were apparently taken in “near-surface recirculation 

piping,” not drain pipes (Weston, 1996b, p. 10). Regarding such utility piping, NIOSH notes that 

“there were other services that traversed the subsurface (e.g., airlines, recirculation piping); 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 20 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

however, NIOSH does not consider work performed in the subsurface at a distance (>5 ft) from 

the drain lines to represent the bounding scenario” (NIOSH, 2023b, p. 6). It is also noteworthy 

that while NIOSH cites all of these survey measurements as “scale data” (NIOSH, 2023b, p. 9), 

the ones cited by Weston for Areas 1 and 4 are for “surface contamination on the interiors of the 

pipes” (Weston, 1996b, p. 10), which supports SC&A’s contention that the in-pipe scale and 

surface contamination terminology appears to have been interchangeable. 

NIOSH: “Locations 4 and 5 accessed lines that had previously supported assay laboratories 

associated with nuclear material manufacturing activities. Sampling and visual observation 

confirmed that these lines had little to no residue accumulation. Analytical data for both CI lines 

showed a total uranium concentration of approximately 500 pCi/g[6] in the thin layer of scale 

[Weston 1996b, PDF p. 17]” (NIOSH, 2023b, p. 9). 

6 507.7 pCi/g of total uranium is cited in table 1 of Weston 1996a (PDF p. 18). 

SC&A response: It is not clear how representative these spot samples may be, coming from a 

limited survey of CI lines supporting one specific Building 10 operation, the assay laboratories. 

This is the source of the “as high as 507.7 pCi/g” cited by NIOSH (2023b, p. 9) for scale 

measurements. However, being collected from drain pipes servicing only one location, it would 

not necessarily be representative of a bounding or even high scale concentration for the full 

scope of Building 10 drain pipes during the residual period. 

NIOSH: “Areas 3 and 4 were identified as having scale and rust with a total uranium 

concentration of 1,864 pCi/g [Weston 1996a, PDF p. 174]” (NIOSH, 2023b, p. 9). 

SC&A response: This survey measurement appears to be for total “bulk material,” that was 

removed from the priority 2 drain lines using a “specially designed vacuum” (table 5.2, Weston, 

1996a, PDF p. 177). Weston noted that “once the loose material and water were removed from 

the line, a hydrolaser was used to remove fixed-surface contamination” (Weston, 1996a, PDF 

p. 177). The cited uranium concentration is for loose debris removed from the Priority 2 drain 

pipes in the form of combined “sediment, debris, scale, [and] rust,” as noted in table 5.2 of 

Weston (1996a, PDF p. 177). The radiological contribution of scale would not have been 

distinguishable from the sediment and other “debris removed from the pipes” (Weston, 1996a, 

PDF p. 177). 

The proposed use of beta scintillator data (from table 3, Weston, 1996b, PDF p. 21) to represent 

scale activity measurements may be of questionable utility as the “geometry of this system is not 

optimal for detecting large accumulations in or around pipes,” but is “adequate for identifying

[but, presumably, not quantifying] contaminated scale within the line” (Weston, 1996b, 

PDF p. 12; emphasis added). It was used in “8 to 10 feedlines” (Weston, 1996b, PDF p. 12), 

specifically for Building 10 locations 23–34 (table 3, Weston, 1996b, PDF p. 21). These 

measurements are direct reading radiological measurements in counts per minute (cpm) with a 

background of 60 to 80 cpm, with results ranging from 71 to 491 cpm (Weston, 1996b, PDF 

p. 21). Such measurements would have suffered from the limitations of direct interior pipe 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 21 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

surface contamination measurements cited by Weston (Weston, 1997a, PDF p. 11; refer to

previous SC&A response in this section). 

Regarding the M&C surface activity calculation method cited in NIOSH’s response (NIOSH, 

2023b, p. 11), Weston’s “SNM License Termination Hypothetical Radiological Dose and 

Exposure Rate Assessment” of Priority 2 drain lines made clear that this methodology was aimed 

at “hypothetical scenarios” that would generate a “hypothetical dose and exposure rate” (Weston, 

1997a, PDF p. 6). The 1997 Weston’s hypothetical radiological dose and exposure rate 

assessment report notes that its methodology relies on combining estimated pipe volumes and 

average densities to “determine the total mass of piping which, when crushed, was available for 

distribution over a surface area thickness of 1 cm (as recommended by NRC),” with the “residual 

total uranium activity . . . [to be] distributed in a thin layer lining the pipes” (Weston, 1997a, 

PDF p. 4). The proposed use of the described “method to calculate surface contamination levels 

on pipe interiors using the thickness of residue lining the pipes and the total uranium 

concentration in the residue” (NIOSH, 2023b, p. 10), as intended for site release, may not be 

sufficiently accurate for purposes of estimating the upper bound source term for scale, 

particularly with the lack of available, representative survey data for interior surface 

contamination. 

SC&A and the WG raise a simple and direct question pertaining to both coagulants and scale that 

goes to the heart of NIOSH’s claims to be able to bound exposures for M&C maintenance 

workers: Does the inside subsurface bounding exposure model adequately reflect and bound 

potential exposures by M&C maintenance workers when cutting, cleaning out, and repairing 

clogged drain pipes at M&C during the entirety of the residual period? The presence of 

contaminated scale on the inside of drain pipes has been confirmed in pre-D&D surveys cited by 

NIOSH in its own evaluation. Is that source term adequately addressed by NIOSH given its 

apparent reliance on high 1995 pre-D&D sediment concentrations to derive a bounding value? 

SC&A finds that not to be the case: While contaminated scale and sediments both figure in preD&D survey results for drain pipes, only the latter was addressed in NIOSH’s bounding model. 

SC&A continues to find the source term issue regarding scale to be credible and substantive. 

NIOSH appears to lack sufficient and representative survey data for in-pipe contaminant scale 

(or interior pipe surface contamination) to provide an adequate basis for an upper bound source 

term for potential exposure of M&C maintenance workers involved with cutting and cleaning out 

these pipes. A single reading as high as 1,000,000 dpm/100 cm2 is supported by only two 

unequivocal scale concentration measurements; these were taken from the same area servicing 

the Assay Laboratory and, therefore, may not be a representative sampling of Building 4 and 10 

drain lines. This is important because NIOSH bases its selection of the 95th percentile 

concentration of 6,887.84 pCi/g on a review of a relatively large and representative sampling of 

uranium sediment measurements taken from the 1995 pre-D&D characterization surveys.

Without other survey measurements, how does NIOSH determine that the “as high as” 

1,000,000 dpm/100 cm2 survey measurement represents the highest value for drainline pipe 

interior surface contamination, including scale, or that higher activity levels would not have 

existed within the M&C drainage system?

As the WG has made clear, for matters of sufficient accuracy the burden resides with NIOSH to 

demonstrate that its exposure models are adequate and bounding. This is not a “demand” that 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 22 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

NIOSH prove a “negative” (NIOSH, 2023b, p. 10). On the contrary, NIOSH needs to address 

substantive source terms and potential exposure pathways that NIOSH itself has identified and 

heretofore has not chosen to reflect in its exposure model. 

4.6 SC&A comment: Bounding exposure pathway

NIOSH’s reliance on “mass-based sample data” and “soil-sampling plans” does 

not address the simple question raised: Given that an AWE hazard assessment 

raised this general worker exposure concern, can this [1,000,000 dpm/100 cm2

] 

potential exposure pathway at M&C be characterized and bounded? This concern 

represents a new issue that has not been addressed. [SC&A, 2023, p. 7] 

4.6.1 NIOSH response: Bounding exposure pathway

NIOSH used the source term concentration calculation from the Bridgeport Brass 

AWE Hazard Assessment [DOE 1996], recommended by SC&A, to calculate an 

inside subsurface dose that incorporates the million dpm survey value that can be 

used to model cutting through a contaminated pipe. . . . 

This calculation shows that adding this one survey result to NIOSH’s other 

subsurface data will increase maintenance worker dose from 71 to 96 mrem 

committed effective dose (CED). 

This adjustment is based on only adding the single value (1,000,000 

dpm/100 cm2) to NIOSH’s dataset. According to Weston [1996b], this was the 

highest surface contamination value, and as shown above, additional data are 

available. Therefore, adding this single value biases the dataset in a very claimantfavorable way (i.e., it increased the 95th percentile by almost a factor of 2).

NIOSH has determined that it has methods for incorporating surface 

contamination data into a bounding method, eliminating the aerosolization of 

drain line contamination as an SEC issue. 

[NIOSH, 2023b, pp. 10–11] 

4.6.2 SC&A response

To clarify, SC&A did not recommend use of any particular source term calculation from, or 

based on, the Bridgeport Brass AWE hazard assessment for purposes of arriving at an estimated 

exposure value. SC&A merely pointed out that NIOSH had heretofore failed to address a 

concern documented in that assessment: “that pipe cutting involving internal [surface] 

radioactive contamination could lead to airborne releases that may involve worker exposure 

(DOE, 1996, PDF p. 48)” (SC&A, 2023, p. 7). 

SC&A supports NIOSH’s recent effort to assess this potential exposure pathway using available 

methods and source term information. However, questions and uncertainties remain.

For example, NIOSH states that “according to Weston [1996b], this was the highest surface 

contamination value,” and referring to the NIOSH response discussed in section 4.6.1 of this 

paper, “additional data are available” (NIOSH, 2023b, p. 11). However, Weston (1996b) never 

claimed that the “as high as 1,000,000 dpm/100 cm2

” (NIOSH, 2023b, p. 8) was the highest in-
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 23 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

pipe surface contamination value at M&C; it happened to be the highest one measured in its 

limited survey of interior pipe surface contamination levels. The “additional data are available” 

(NIOSH, 2023b, p. 10) consideration was addressed in section 4.6.1 of this paper, but these data 

are few in number, some are not applicable, and, overall, they are not a representative 

characterization of interior pipe surface contamination of the M&C drain pipe system. Therefore, 

reliance on a single data point from one portion of a single pipe (Area 7, initiation point of a 4-

inch VC mainline) may not be sufficiently accurate for deriving a source term for this exposure 

pathway. 

It should be noted that the source term values for the Bridgeport Brass hazard assessment were 

based on “actual U-238 surface activity measurements” at that site (DOE, 1996, PDF p. 47), with 

a uranium (U) dose conversion factor assuming “an activity-weighted average for natural 

uranium, based on the U-238, U-234, and U-235 natural radioactivity ratio of 1:1:0.046” (DOE, 

1996, PDF p. 42). This contrasts with the single cited interior pipe surface activity measurement 

for M&C that likely contained a higher fraction of U-235, backed by a few spot scale 

measurements. 

In this case, the uncertainty also extends to the derivation of “T,” thickness of interior pipe 

surface activity. As noted in the DOE hazard assessment, the “selection of the thickness of the 

contamination layer is a significant uncertainty for the hazard assessment,” with DOE’s selection 

of T for Bridgeport AWE based on “a conservative estimate developed based on literature 

values, and information related to the cleanup methods for this site [Bridgeport]” (DOE, 1996, 

PDF p. 47). In applying DOE’s parameter for surface activity thickness in its calculation, it is 

unclear what M&C-specific information could and should have been applied by NIOSH based 

on M&C interior surface activity thickness within drain pipes. However, without some basis in 

actual M&C measurements and experience, any calculation may not be sufficiently accurate for 

exposure modeling. 

First, the fixed surface contamination present at Bridgeport was for carbon steel, with little 

assumed penetration, and a thin layer of residual surface contamination because those pipes had 

been “cleaned using high pressure wash systems” (DOE, 1996, PDF p. 47). This differs from the 

M&C case, where the as high as 1,000,000 dpm/100 cm2 value was apparently sampled using 

smears7 from a PVC pipe containing surface contamination that had not been previously washed 

and was obviously not fixed contamination. 

7 SC&A did not find a specific reference to the sampling method that resulted in the up to 1,000,000 dpm/100 cm2

measurement but is relying on NIOSH’s statement about it that “it is appropriate to use mass-based sample data 

(e.g., pCi/g) to characterize the exposure environment,” as it permits the development of “models more 

representative of the subsurface work than do swipes of surface contamination” (NIOSH, 2021, p. 7). 

Second, unlike Bridgewater, the thickness and density of in-pipe surface contamination would 

have been influenced by the unique physical and chemical characteristics of M&C drainpipe 

discharge. Of particular note was the regular release of an oil-based coagulant to the drain lines, 

which may have induced scale and other contaminant buildup on the interior of pipes that would 

have influenced the thickness and density of surface activity. Surface activity composition, 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 24 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

density, and thickness may have been significantly different for M&C than those experienced at 

Bridgeport or any other AWEs due to the regular presence of this coagulant. 

These and other uncertainties are presumably the basis for NIOSH adding additional 

conservatism—e.g., “increased the 95th percentile by almost a factor of 2” (NIOSH, p. 11)—as 

part of its “extreme conservatism” approach. However, the sufficient accuracy and, ultimately, 

plausibility of this approach are questionable. 

5 Work in Confined Spaces

5.1 SC&A comment: Routine drain line repair in pits or trenches (6-month 

occupancy)

As emphasized in former worker interviews, it was not uncommon to be working 

in a trench doing routine utility repairs or pipe cleanouts for days and up to a 

week (NIOSH, 2017b, pp. 1–2). One installation project in Building 10 involved 

the cutting out of an existing drain line and installation of new equipment, piping, 

and large tanks, necessitating a trench 100 feet long, with a depth of 8–10 feet in 

places, that was worked in for 6 months in 1983–1984 ([ORAUT, 2017c], p. 11). 

[SC&A, 2023, p. 8] 

5.1.1 NIOSH response: Routine drain line repair in pits or trenches (6-month 

occupancy)

There appears to be some misinterpretation in SC&A’s description of work 

performed in confined spaces that requires clarification. SC&A stated that M&C 

workers were performing confined space work for six months, presumably to 

install the Beckett line mentioned in the following interview excerpts. [NIOSH, 

2023b, p. 13] 

NIOSH proceeds to cite various interviews that indicate that workers were not actually within the 

confined space for the full 6 months and that their presence in the Beckett line trench actually 

involved periodic work activities that were, in general, about 200–300 hours per year “inside a 

hole” (ORAUT, 2017c, PDF p. 19), with the duration of work being about a week at a time. This 

level of activity also reflected reliance on outside contractors for much of the excavations.

NIOSH summarized that the main points from the worker interview include the following 

(NIOSH, 2023b, p. 17): 

• Maintenance workers using a snake while standing on the undisturbed 

concrete floor, addressed probably more than 60% of clogged drains (i.e., 

primary source term).

• “Stage 3” excavations, (i.e., when the snake did not work), happened 

approximately once a year. 

• Contractors, not maintenance personnel, cut the concrete using a wet process 

and excavated the hole for the Beckett Wire machine with a backhoe. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 25 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

• A pump was needed to remove the water from the wet subsurface 

environment. 

• Once excavated, the contractors lined the hole with clean dirt, and M&C 

workers installed the equipment on top of the clean fill.

• Of the various M&C groups, Facilities personnel spent the most time 

performing subsurface work, which amounted to less than two months per 

year.

5.1.2 SC&A response

SC&A did not misinterpret the available information regarding the Beckett line work. This was 

an SC&A comment based on a worker interview conducted by NIOSH (ORAUT, 2017c, p. 12) 

that there had been one installation that “involved cutting out an existing drain line and installing 

new equipment, piping, and large tanks, necessitating a trench 100 feet long, with a depth of 8–

10 feet in places, that was worked in for 6 months in 1983–1984” (SC&A, 2022, p. 32). This 

worker citation (ORAUT, 2017c) was included in the supplemental review to illustrate that not 

all subsurface excavation work at M&C during the residual period was small, short-duration 

utility replacement or repair work. NIOSH infers that SC&A interprets that M&C workers would 

have been present continuously within the Beckett line trench during the entire 6 months of 

excavation and installation, but that was not SC&A’s interpretation. Given the nature and history 

of M&C maintenance work, that would not make sense nor does that comport with SC&A’s 

citations in the supplemental review that noted that “the work involved considerable time, 

usually days, but sometimes a week at a time ([NIOSH, 2017b], p. 2) and up to 6 months for one 

project ([ORAUT, 2017c], p. 11)” (SC&A 2022, p. 12). The work was intermittent and task 

related and would have been performed as such for the duration of the 6-month subsurface 

project.

5.2 SC&A comment: Confined spaces standard

SC&A previously supplied a confined space definition: 

OSHA defines confined spaces and cites examples including pits, tanks, silos, 

maintenance holes, sewers, enclosed drains, and manholes . . . . OSHA notes that 

pits, although typically open on top, can be completely underground or below 

grade and can still be a confined space (OSHA, 2015). Supporting industry 

literature following promulgation of the Subpart AA standard noted that confined 

spaces “include tight work areas with reduced air flow” where work such as 

“welding, cutting, grinding, sanding or any high-energy activity can create . . . 

respirable particles and/or toxic aerosols (Chase, 2019).” [SC&A, 2022, p. 32] 

5.2.1 NIOSH response: Confined spaces standard

Although there were confined spaces at M&C, the concern within the EEOICPA 

program is only for those with a radiological hazard. The source term of primary 

concern at M&C was the drain lines in the subsurface of Building 10. The Weston 

[1996b] drainage system characterization describes that system as follows:
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 26 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Buildings 4 and 10 drainage systems consist of 4-inch vitreous clay (VC) 

and 4, 5, and 6-inch cast-iron (CI) lines (referred to as “arterial lines”) 

located 2 to 3 feet below facility Grade. [PDF p. 7]

Considering the Weston [1996b] statement above, NIOSH does not consider a 

Facilities worker spending two months during a particular year working on a drain 

line in such a shallow hole to have performed that work in a confined space. 

For the remaining 40% of the time when the snake would not work, workers had 

to dig ~3 feet to access the clogged pipe. A safety professional would not control 

this work as a confined space entry, especially in an industrial facility with active 

ventilation. The hole is too shallow to “include tight work areas with reduced air 

flow” as the reference SC&A provided above states. Furthermore, as pointed out 

in the SNM License Termination Radiological Dose Assessment, “Scenario 

assumptions for ventilation and work times understate the true dilution effects of 

ventilation” [Weston 1997b, PDF p. 14]. M&C had two exhaust fans that 

ventilated and removed air from Building 10. One ventilation stack equipped with 

a high-efficiency filter exhausted air from the press room at a rate of 616 ft3

 per 

minute (cfm), and another stack exhausted air from the furnace area at a rate of 

500 cfm [Texas Instruments 1979, PDF p. 20]. 

Within the OSHA confined space standard, there are no strict definitions as to the 

exact depth required to designate, which allows room for professional judgment. 

However, standard practice indicates that safety professionals would not control a 

3.5-foot-deep trench dug to service a drain line as a confined space. In general, 

work on the drainage system, identified as the worst-case exposure scenario for 

maintenance workers, would not have been performed within a confined space 

work environment. 

[NIOSH, 2023b, pp. 17–18] 

5.2.2 SC&A response

The reason SC&A raised this issue is that confined spaces restrict the movement of air in work 

spaces such that fumes and particulates released into those spaces can concentrate and pose 

increased inhalation exposure concerns—and notably increased airborne concentrations—for 

workers within those spaces. The ergonomics of the work matters. If workers must crouch and 

bend over to conduct their work within a trench of even 3.5-foot depth, as would M&C 

maintenance workers cutting, cleaning, and replacing drain pipes, the breathing zone of those 

workers would have been closer to the bottom of the trench (adjacent to the pipes) and affected 

by confined space atmospheres in terms of the concentration of particulates and fumes. While 

there would have been building ventilation in Building 10, it is unlikely to have made much 

difference within the work trenches involved, whether the 3.5-foot drainline trenches or the 8–

10-foot Becket line installation trench. 

To address these circumstances, a revised resuspension factor (and dust loading factor) is needed 

as indicated in SC&A’s supplemental review (SC&A, 2022, p. 32): 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 27 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

To illustrate, while NIOSH applies a standard 10-6 m-1 resuspension factor in its 

OTIB-0070 evaluation, the International Atomic Energy Agency (IAEA) 

guidelines for “Radiological Aspects of Non-fixed Contamination of Packages 

and Conveyances” recommends a resuspension factor of 4×10-5 m-1 for dusty 

operations in confined spaces (IAEA, 2005, p. 11).24 [24 IAEA-TECDOC-1449 

references the Fairbairn model, which applies other parameters for modeling 

airborne contaminants. It is unclear how these parameters relate to similar OTIB0070 considerations, although it does appear more conservative regarding 

confined spaces.] The U.S. Department of Energy (DOE) “User’s Manual for 

RESRAD-BUILD Version 3” gives a resuspension factor of 4.3×10-5 m-1 for 

“active work in confined, unventilated space” (Argonne National Laboratory, 

2003, p. J-33).

These considerations also reinforce finding 2 of SC&A’s supplemental review, that “the 

application of surrogate data from the Mound project to provide a dust-loading factor for M&C 

subsurface activities does not satisfy the Board’s surrogate data policy” (SC&A, 2022, p. 33). 

The Mound project data do not reflect any consideration of reduced ventilation within trenches, 

pits, and vaults within which intrusive maintenance activities were conducted. The air 

monitoring data collected for that study were taken at a distance from the excavation (15–20 feet 

away) (NIOSH, 2020c, p. 6) and are, therefore, not equivalent to the more confined spaces 

within which M&C workers conducted their pipe cutting, cleanouts, and replacement. 

5.3 SC&A comment: Confined spaces and work not associated with drain line 

cleaning

While the 1995 drain line sediment reading is a high concentration level, can it be 

applied as a bounding exposure for unrelated inside subsurface work (i.e., nondrain line cleaning) for which little, if any, information is available and for which 

confined space atmospheres were involved? [SC&A, 2022, p. 21] 

5.3.1 NIOSH response: Confined spaces and work not associated with drain line 

cleaning

The following is SC&A’s summary of the NIOSH (2023b) response on pages 19–25, which 

included figure 1, “Building 10 – Affected Areas,” and figure 2, “Building 10 Pipe Grouping for 

Uranium-235 Inventory Development.” According to NIOSH (2023b, pp. 18–19): 

NIOSH acknowledges there were confined spaces at M&C. However, the key 

consideration is whether there were contaminated confined spaces associated 

with the Building 10 subsurface where M&C workers incurred exposures that 

represent a plausible scenario for which NIOSH cannot bound doses. NIOSH 

finds: 

• The pathway for contaminants to get to the subsurface was through the floor 

drains, and to a lesser extent, through cracks in the concrete when the floor 

flooded, and contaminants got washed into the subsurface. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 28 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

• The subsurface is well described and shows that after contaminants flowed to 

the subsurface, they generally stayed within 5 feet of the drainage system 

network of pipes, which were approximately 3-feet deep.

Interviewees described subsurface work that included some confined space work; 

however, their recollections included work in other buildings and areas not 

associated with the source term. When workers did describe work in Building 10, 

they referred to the entire building and did not differentiate whether their work 

was in the part of the building that contained the source term of primary concern: 

Priority 1 drain lines. This is an important distinction because nuclear 

manufacturing operations were primarily performed in the northern third of 

Building 10, and support activities, including transportation and storage, were 

performed in the balance [Weston 1996a, PDF p. 10]. 

NIOSH elaborates that “the area of Building 10 with the Priority 1 drain lines is small compared 

to the rest of the building,” as illustrated by two diagrams of “Building 10 – Affected Areas” and 

“Building 10 Pipe Grouping for Uranium-235 Inventory Development” (NIOSH, 2023b, p. 19). 

NIOSH (2023b, pp. 23–24) summarized that: 

M&C evaluated exposures to maintenance workers using pre-D&D survey data, 

developed a bounding scenario for all work activities except those associated with 

Priority 1 drain lines, and calculated a dose of <1 mrem. Conservatively, NIOSH 

applies its model to all subsurface work at M&C, including work in most of 

Building 10 that was not associated with the Priority 1 drains.

Regarding SC&A’s concern about other types of work, when M&C did perform 

other work, such as replacing large pieces of machinery, they (or contractors) dug 

deeper holes. There is some potential that contaminants migrated into some of 

those soils, especially if they were close to a drain line. However, NIOSH does 

not consider that work extensive enough to be selected as the plausible bounding 

scenario.

5.3.2 SC&A response

The context of SC&A’s comment (and its original finding 2 from the supplemental review) 

relates to the use of the Mound project data as a basis for the dust loading factor for M&C-wide 

exposure modeling, and the concern that it does not reflect the effect of confined spaces on the 

resuspension and concentration of airborne particulates and fumes. NIOSH has responded that it 

is committed to reviewing recent suggestions to upgrade its dust loading models, including 

enhancement factors and confined spaces, and will consider incorporating methods suggested by 

SC&A in their supplemental review. While the issues raised by NIOSH (e.g., proportion of 

operating buildings affected by confined spaces, proximity to radiological sources, and degree of 

contamination) are mitigating considerations, they would not change the overriding finding by 

SC&A that the proposed sitewide dust loading factor for M&C, as based on the Mound 

excavation project data, does not meet the Board’s surrogate data policy in terms of equivalent 

site conditions.
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 29 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Regarding the issue of other types of work (i.e., “non-drain line cleaning” (SC&A 2022, p. 21)), 

specifically the repurposing of large pieces of equipment, we address NIOSH’s response in 

section 7.4 as part of our response to the WG’s concern about AWE equipment. 

5.4 SC&A/Work Group comment: Applying Mound surrogate data to dust 

loading factor

SC&A commented:

NIOSH does not respond to the central question posed: In applying the Mound 

surrogate data to derive a dust loading factor, did they address confined space 

considerations? From a larger perspective, did they consider the impact of 

confined spaces on their modeled airborne resuspension of uranium and thorium? 

The answer appears to be “no” in both cases. Confined spaces represent a new 

issue that has not been addressed. [SC&A, 2023, pp. 8–9] 

At the July 13, 2023, WG meeting, a Board member presentation stated (ABRWH, 2023a, 

slide 19): 

• . . . M&C maintenance workers doing subsurface work routinely had to snake 

out and repair (cut, saw, grind, weld) underground pipes. 

• These routine components of M&C operations also created additional sources 

of radioactive dusts and particulates, beyond those from the (Mound-based) 

dust-loading.

• The current NIOSH bounding model does not appear to account for these and 

should. 

As the Board member explained (ABRWH, 2023a, slides 16–17): 

The Mound database: Collected under different conditions than the M&C 

subsurface trenching

• The Mound project trenching data were collected outdoors on a country lane, 

whereas the M&C maintenance subsurface exposures, of course, took place 

indoors in Building 10. 

• As such, using the Mound data as surrogates for M&C violates one of the 

Criteria for the Use of Surrogate Data, adopted by the Board in 2014. . . . 

The Mound database seems a poor fit for M&C 

Because of the major differences in work environments between Mound and 

M&C – an outdoor, relatively placid country lane vs. an indoor, dirty, often 

muddy industrial worksite, respectively – this WG member believes the Mound 

database is a poor fit for M&C surrogacy.
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 30 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

5.4.1 NIOSH response: Applying Mound surrogate data to dust loading factor

The hazards associated with working in confined spaces are not new to the field 

of industrial hygiene and were also recognized by M&C personnel. NIOSH is 

committed to reviewing recent suggestions to upgrade its dust loading models, 

including enhancement factors and confined spaces, and will consider 

incorporating methods suggested by SC&A in their supplemental review. In 

addition, as discussed by SC&A in SC&A Commentary on NIOSH’s Approach to 

Quantifying Outdoor and Indoor Airborne Dust Loadings, airborne contamination 

levels can be modeled (i.e., bounded) up to a choking level [SC&A 2021, PDF 

p. 22], making the confined space effect on dust loading factors a TBD issue and 

not an SEC issue. This addresses SC&A’s remaining issue with applying the 

Mound surrogate data to derive a dust loading factor. [NIOSH, 2023b, p. 24] 

5.4.2 SC&A response

SC&A stands by its original finding 2 (SC&A, 2022) that NIOSH’s proposed application of 

Mound project data for deriving the M&C dust loading factor does not satisfy the Board’s 

surrogate data policy for site and process similarity given disparities between the sites for 

confined space conditions. The use of the Mound-based dust loading factor, as one of the three 

“legs of the stool” (ABRWH, 2023b, slide 15) for NIOSH’s bounding intake approach for M&C 

may not be sufficiently accurate for that reason. 

In support of its finding, SC&A provided examples of resuspension factors developed by 

national and international standards bodies based on experience with the effects of confined 

space atmospheres in working environments. In doing so, SC&A clearly acknowledges that this 

issue, by past practice and experience, is a TBD issue for which there are obviously means and 

information by which a more accurate dust loading factor can be derived. NIOSH does not 

directly accept or acknowledge that the Mound data should not be applied, as currently derived, 

but does accept that it will need to review “recent suggestions to upgrade its dust loading models, 

including enhancement factors and confined spaces, and will consider incorporating methods 

suggested by SC&A in their supplemental review” (NIOSH, 2023b, p. 24). 

In its response to the WG on this issue (NIOSH, 2023b, pp. 33–35), NIOSH cites the 

contributions of Dr. Lynn Anspaugh to the “SC&A Commentary on NIOSH’s Approach to 

Quantifying Outdoor and Indoor Airborne Dust Loadings” (SC&A, 2021) regarding the use of 

the Mound surrogate data at M&C. In that review, SC&A concluded that “the renovation indoor 

dust loading of 10-4 g/m3 (100 μg/m3) might include excavation and would seem to 

independently support NIOSH’s use of 212 μg/m3 as a reasonable estimate when applied to the 

M&C subsurface indoor excavation scenario and also to indoor excavation dust loading in 

general” (SC&A, 2021, p. 18).

As noted in SC&A’s supplemental review and later responses, SC&A does not dispute the 

scientific validity of Dr. Anspaugh’s work in support of SC&A’s past review of the Mound dust 

loading factor, just that the Mound Study air monitoring was performed 15–20 feet away from 

the actual trench excavation and its air sampling results would not have been representative of 

the increased particulate resuspension expected within the trench due to confined space effects.

This was the basis for SC&A’s finding that the Mound study data would not satisfy the Board’s 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 31 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

surrogate data policy because such monitoring information was not obtained in an equivalent 

manner as that of trenches and other confined space circumstances at M&C.

With SC&A’s acknowledgment that this is essentially a TBD issue and NIOSH’s acceptance that 

it will need to review SC&A’s suggested options to revise its dust loading models for M&C, 

SC&A recommends that the issue of the dust loading factor for M&C be pended for resolution 

by the WG awaiting the results of that review.

6 Additional Intrusive Activity Information for Table 1, Comparison of 

AWE Sites

6.1 NIOSH summary of SC&A table 1 and response (table 2 of NIOSH, 2023b)

In the Supplemental Review of M&C Work Group Issues [SC&A 2022], SC&A 

provided a table with the following five column headings: (1) AWE site, 

(2) source of exposure potential, (3) intrusive work activity (covered), (4) SEC 

class designated, (5) and reference. During the May 12, 2023, M&C Work Group 

meeting, NIOSH indicated it would provide information that could serve to 

update Table 1 with additional detail concerning intrusive activities and dose 

potential. [NIOSH, 2023b, p. 24] 

NIOSH provided table 2, “Additional Information to Augment SC&A’s Comparison of AWE 

Sites Table 1” (NIOSH, 2023b, pp. 25–29). 

6.1.1 SC&A response

While SC&A has no reason to dispute the additional information provided by NIOSH to 

illustrate some of the additional intrusive activities that took place at other AWEs, it is unclear 

what NIOSH’s purpose is for providing it at this time. An earlier AWE-by-AWE assessment in 

response to a WG question elicited a similar NIOSH response (NIOSH, 2020a, p. 13): 

NIOSH Conclusion: M&C operations were similar to operations at these other 

sites. Uranium was machined at most of these sites; thorium is documented to 

have been at over half of them. Residual-period tasks performed by workers at 

these other sites, including contaminated soil excavation and welding and torchcutting in contaminated areas, have been evaluated. The pathways leading to 

internal exposures from alpha-emitting radionuclides such as uranium and 

thorium are identical for workers at all of these sites: the inhalation and ingestion 

of resuspended, contaminated dust. 

The methods proposed for M&C by NIOSH and SC&A are similar and consistent 

with those previously approved by the Board to bound worker exposures during 

residual periods, including developing ratios between materials with known 

concentration data and materials with historically unmeasured concentrations. 

The types of radioactivity, the crafts personnel who worked with it, and the tasks 

performed are found across all of the AWE sites. The worker radiation exposures 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 32 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

and the applicability of the bounding methods during the M&C residual period do 

not stand out as unusual amongst AWE sites. 

Although the procedures used by NIOSH [ORAUT 2012] appear to be designed 

for routine exposures, NIOSH and the Board have adapted and relied upon them 

to bound non-routine exposures, such as those that occurred during M&C 

maintenance, or at other AWEs with foundries and steel mills.

The intent of SC&A’s supplemental review table 1 was to take exception to this broad 

characterization by contrasting the pronounced and protracted level of intrusive activities by 

M&C maintenance workers during the residual period to those of workers at other AWEs.

SC&A’s disagrees with NIOSH’s conclusion in its 2020 response that “the pathways leading to 

internal exposures from alpha-emitting radionuclides such as uranium and thorium are identical 

for workers at all of these sites: the inhalation and ingestion of resuspended, contaminated dust” 

(NIOSH, 2020a, p. 13). It is clear to SC&A, as highlighted in its supplemental review and 

subsequent papers, that M&C’s maintenance activities more closely resembled the renovation 

activities highlighted in NUREG/CR-5512 rather than the passive exposure scenarios based on 

contaminant resuspension derived from OTIB-0070 and TBD-6000 for these other sites. As 

noted by SC&A in its April 2023 response paper: 

While the question of how intrusive work activities may have been at M&C is 

obviously a subjective one, SC&A believes there is clear evidence that 

maintenance activities during the M&C residual period were unique in terms of 

their level of intrusiveness (excavations, pipe cleaning, pipe cutting), work 

environments (confined spaces), and uncertain or unknown source terms 

(contaminated pipe sediments, presence of coagulants, contaminated scale, 

confined space concentration of airborne particulates). While other AWE sites, 

such as Carborundum and Dow Madison had residual work activities (e.g., 

welding, torch-cutting, soil excavation) similar to those of M&C maintenance 

workers, the difference is the aforementioned level of intrusiveness and uncertain 

or unknown source terms. Ultimately, NIOSH acknowledges the “high exposure 

conditions” and “unknown contamination sources” that may have been associated 

with such M&C intrusive activities (NIOSH, [2023a], p. 17) in developing its 

bounding models. [SC&A, 2023, p. 11)] 

The fact that workers at other AWEs performed, for example, general machine shop 

maintenance, periodic lathe grinding, routine steel plant maintenance, periodic excavations, and 

soil removals, and handled heavy equipment, as outlined in NIOSH’s table 2 (NIOSH, 2023b, 

pp. 25–29), is not surprising, but these activities do not rise, in SC&A’s judgment, to the level, 

nature, and frequency of intrusive activity that typified M&C maintenance activities. 

SC&A’s judgment appears to be supported by the basis for NIOSH’s original decision to 

consider specific exposure models to address worker-identified exposure pathways at M&C that 

were sufficiently intrusive as to be inconsistent with assumptions based on OTIB-0070 and 

TBD-6000 resuspension methods (NIOSH, 2018, p. 2):
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 33 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

From October 24 through October 26, 2017, NIOSH, Oak Ridge Associated 

Universities (ORAU), and Sanford Cohen & Associates (SC&A) personnel 

interviewed 12 former M&C workers and individuals knowledgeable about 

maintenance work. Interviewers asked questions regarding the frequency and 

duration of work, including HVAC, utility and drain line maintenance, and new 

equipment installations. During the interviews it became apparent that Building 

10 experienced recurring issues with water drainage (ORAUT [2017a], PDF p. 6; 

[2017b], PDF p. 5; [2017c], PDF p. 8; [2017d], PDF p.7; [2017e], PDF, p. 5) and 

underwent multiple equipment change-outs that necessitated subsurface and 

overhead work. Although this work was sporadic and sometimes emergent in 

nature, it exposed workers in a manner that did not agree with the method 

described in the SEC-00236 ER (i.e., surface contamination resuspension).

[Emphasis added.] 

While all of these AWEs (for their residual periods, with the exception of Norton, Linde, and 

Vitro) did not necessitate special bounding models for any of the intrusive activities mentioned 

in table 2 (NIOSH, 2023b, pp. 25–29), M&C required no less than six such models to address 

intrusive activities that could not be readily bound by the more passive resuspension and 

exposure assumptions available in OTIB-0070 and TBD-6000. SC&A does not question 

NIOSH’s ability to adapt such methods designed for more passive exposure scenarios to what are 

clearly unique and substantial intrusive activities at M&C but does disagree with the 

generalization that M&C’s maintenance activities were little different than those found during 

the residual periods for these other AWEs. 

SC&A finds that some of the residual period activities noted by NIOSH for these other AWEs 

bear some resemblance to those at M&C. However, by its action to derive six exposure models 

for M&C, NIOSH itself acknowledges that these intrusive maintenance activities were 

sufficiently distinct from the assumed passive scenarios of OTIB-0070 and TBD-6000, and 

differed from experience at other AWEs, to warrant special treatment from an exposure 

bounding standpoint. 

7 M&C Work Group Concerns

NIOSH selected specific concerns to address based on WG concerns expressed during its recent 

deliberations and presentations. SC&A addressed those that have been raised previously in its 

reviews and responses in support of the WG. This paper addresses issues such as worker 

protection, claimant-favorable assumptions (i.e., extreme conservatism), and confined spaces in 

the sections centered on those topics. Sections 7.1–7.6 address the balance of issues raised by 

NIOSH as WG concerns, for which SC&A has previously provided comments, and for which 

Board review and judgement would be rendered. 

7.1 Work Group concern: Data applicability

The following excerpts show data applicability concerns that have been presented at recent

Advisory Board and M&C WG meetings. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 34 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

The M&C WG Chairperson’s presentation at the August 16, 2023, Advisory Board meeting: 

• NIOSH applies 1995 D&D survey data as basis for an upper bound for 

residual period exposure. For radiological data from one time period to be 

considered informative about exposures during another time period, there 

should be sufficient similarity of conditions and processes between the two 

periods. [ABRWH, 2023b, slide 19] 

A Board member’s presentation at the July 13, 2023, M&C WG meeting:

• M&C maintenance workers were given no radiological health and safety 

(H&S) information or training during the residual period, and only 

occasionally received personal protective equipment (PPE). Also, after 1983, 

following the NRC’s removal of radiation work restrictions for Building10, 

they believed they were not working under hazardous radiological conditions. 

• Thus, certainly after 1983, M&C maintenance workers could not be expected 

to have followed the ordinary, common-sense precautions that any intelligent 

person would follow when working on and near the piping in a potentially 

hazardous radiation environment.

• The Result: The M&C maintenance workers would be expected to experience 

greater doses of radiation than assessed in the NIOSH bounding model. 

[ABRWH, 2023a, slide 10] 

7.1.1 NIOSH response: Data applicability

If NIOSH identified air monitoring during an operation (e.g., grinding) in one 

time period and tried to apply that data to a different time period and operation 

(e.g., welding), then the Work Group’s concern could be valid. Similarly, if 

NIOSH used Priority 3 drain line data to bound exposures during work with the 

Priority 1 source term, then again, the Work Group would have a valid data 

applicability argument. On the contrary, NIOSH validated a bounding source term 

(pre-D&D to the extent a fuel pin was still present) and applied appropriate 

resuspension/dust loads for the various operations described by interviewees.

Furthermore, one of the primary reasons the Weston [1996b] drainage system 

characterization (the report where NIOSH obtained the subsurface data) was 

performed before D&D in 1995, was to quantify the risk to ongoing drain line 

maintenance workers as documented in the following excerpt: 

The drainage system investigation was performed immediately after the 

Pilot-Scale Interiors Remediation Project and prior to the Full-Scale 

Interiors Remediation Project. An aggressive investigation schedule was 

implemented in support of Nuclear Regulatory Commission (NRC) license 

termination and to assess the potential for inadvertent exposures to nonradiological workers performing routine drainage system maintenance.

[Weston 1996b, PDF p. 7] 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 35 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

The excerpt above confirms that drain line maintenance was still being performed 

at the time of the 1995 survey. In fact, after these data were obtained, and because 

of the results, M&C implemented controls on future drain line maintenance using 

three levels of priority designation [Weston 1996b, PDF p. 29]. 

Although the frequency of clogged drains may have increased over time as the 

building aged, the techniques employed to unclog drains did not change 

throughout the residual period (i.e., snake technology did not change significantly 

from 1968 to 1995). 

[NIOSH 2023b, pp. 30–31] 

7.1.2 SC&A response

A central thesis of SC&A’s supplemental review for M&C is founded on the Board’s 

deliberations during the Linde Ceramics SEC review:

The use of a high exposure or concentration value based on a set of specific 

workplace [pre-D&D sediment] data to bound or represent that of other workers 

in a facility or on a site, particularly over a lengthy time period, would not be 

appropriate if their exposure potential could be higher, conditions were different, 

or if there is a lack of information upon which to make that judgment. [SC&A, 

2022, p. 36] 

In testing this thesis, SC&A made several key findings that highlighted conditions or processes 

that would have potentially affected the source term for M&C maintenance worker exposure 

during the residual period that were not considered in the application of the 1995 pre-D&D data 

in NIOSH’s exposure modeling. 

SC&A found that coagulant oil could have introduced higher concentrations of covered uranium 

and thorium from AWE operations into the drains, specifically during Wire Department 

operations in Building 10 up through 1981. NIOSH initially disputed this finding but now has 

“determined that it can describe plausibly, and bound exposures associated with unclogging 

pipes while accounting for the effects of introducing a nonradioactive coagulant to the drain line 

source term” (NIOSH, 2023b, p. 5). This conclusion is premised on a series of explanations and 

assumptions that SC&A has not accepted as valid (refer to the preceding discussion regarding 

coagulants in section 3). As SC&A emphasized in its supplemental review and subsequent 

responses, the regular discharge of a known coagulant into the M&C drainage system during 

Building 10 operations that led to the cited clogging of pipes represents a condition and process 

that would have potentially consolidated and concentrated existing uranium and thorium within 

the drainage system in the earlier M&C residual period, which may have led to an elevated 

source term not addressed by NIOSH’s inside subsurface exposure model. 

SC&A found that that cutting of drain lines with contaminant scale found to be as high as 

1,000,000 dpm/100 cm2 may be a systemic issue for M&C exposure potential, a concern 

exemplified by DOE in its hazard assessment for the Bridgeport Brass AWE. NIOSH disputes 

that this is a systemic issue at M&C but has provided only that single high measurement and a 

few spot samples of scale contaminant measurements to back its claim.
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 36 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

The cutting, cleaning out, and repair of piping with such interior surface contamination levels 

would have led to the likely volatization and airborne suspension of such contaminants into the 

breathing zone of maintenance workers performing these intrusive activities. This condition and 

exposure pathway are not addressed by NIOSH in its existing inside subsurface exposure model 

based on resuspension of contaminated sediment as the bounding source term (though NIOSH 

has now performed a cursory exposure analysis based on parameters from DOE’s Bridgeport 

Brass hazard analysis).

Regarding confined spaces, SC&A stands by its original finding 2 (SC&A, 2022) that NIOSH’s 

proposed application of Mound project data for deriving the M&C dust loading factor does not 

satisfy the Board’s surrogate data policy for site and process similarity given disparities between 

the sites for confined space conditions. Therefore, the use of the Mound-based dust loading

factor as one of the three “legs of the stool”8

8 The other two are source term and occupancy/time. 

(ABRWH, 2023b, slide 15) for NIOSH’s bounding 

intake approach for M&C may not be sufficiently accurate for that purpose. While not a data 

back-application issue, it raises a similar data applicability concern. While NIOSH continues to 

dispute the significance of this issue for its dust loading model, it has agreed to review “recent 

suggestions to upgrade its dust loading models, including enhancement factors and confined 

spaces, and will consider incorporating methods suggested by SC&A in their supplemental 

review” (NIOSH, 2023b, p. 24).

NIOSH questions the distinction SC&A draws between how the exposure potential of D&D 

workers would have been less than M&C maintenance workers when performing pipe cutting 

and removals. However, its January 2023 response paper (NIOSH, 2023a) references a worker 

account that supports the interpretation that the latter’s job was also to clean the pipe prior to 

repair (versus removal for D&D), and that, therefore, there would have been a difference in 

physical proximity and source term. It is clear to SC&A that M&C workers performed more 

intrusive work with more proximity of exposure, without the radiological controls that would 

have mitigated that exposure. 

The preceding forms a key basis for SC&A’s finding 1 that “the back application of a high 1995 

sediment survey result to bound inside subsurface activities is not adequately supported by 

information for M&C worker activities from the earlier residual time period” (SC&A, 2022, 

p. 36). NIOSH’s interpretation of data applicability, specifically the conditions and processes in 

place during the 27-year M&C residual period versus those in 1995 (when the pre-D&D 

sediment samples were obtained), is in question here. While these 1995 source term 

concentrations, at the 95th percentile, were deemed by NIOSH as the upper bound for all 

workers conducting maintenance work inside M&C buildings, SC&A has taken issue with 

whether facility conditions and processes during the residual period may have been sufficiently 

different than those in 1995 to compromise this back-application of radiological source term. 

7.1.2.1 Linde Ceramics precedent

The precedent for this concern can be found with the Linde Ceramic SEC Board 

recommendation and U.S. Department of Health and Human Services (HHS) designation of the 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 37 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

SEC class for Linde’s renovation period. As with M&C, NIOSH believed it had sufficient and 

representative D&D-era data to apply to the prior residual period (HHS, 2011, p. 4): 

Based on available Linde decontamination and decommissioning (D&D) survey 

data and residual radiation surveys conducted in association with FUSRAP 

activities, NIOSH believed it had the necessary data to support bounding internal 

exposures for uranium, uranium progeny, and radon during the residual period. 

Radioactive operations terminated at the end of the operational period and sourceterm materials were removed from the site. NIOSH’s position was that the 

application of these survey data would result in overestimates of doses during 

general activities, as well as during the highest potential exposure conditions for 

the period evaluated in the ER (January 1, 1954 through July 31, 2006). 

As with M&C’s residual period, NIOSH had proposed to apply D&D-era survey data as the basis 

for developing an upper bound source term for Linde’s renovation period (HHS, 2011, p. 4): 

NIOSH has determined, and the Board concurred, that there was the potential for 

exposure to significant dose levels during the renovation period from 1954 

through 1969. To account for this potential of exposure, NIOSH proposed using 

survey data taken during the decontamination activities (which took place during 

the operational period) as the basis for developing an upper bound for the 

exposure. In order for radiological data from one time period to be 

considered informative about exposures during another time period, there 

should be some similarity of conditions and processes between the two 

periods. The NIOSH ER regarded the decontamination activities at the end of the 

operational period to be sufficiently similar to renovation activities during the 

residual period. Therefore, NIOSH believed that radiological data from the former 

were informative about exposures during the latter. Although NIOSH has 

proposed claimant-favorable dose reconstruction methods in its ER for workers at 

the Linde site during the renovation period, the uncertainty (as discussed by the 

Board) concerning what activities actually took place during renovation and 

the impact such activities might have had on the resulting dose levels suggests 

that the dose reconstruction methods may not account for all exposure 

scenarios during building renovation. [Emphasis added.] 

The pipe cutting and cleaning activities may have been similar over time, but the conditions and 

processes would have varied due to potentially different source terms and exposure pathways 

during the pre-1995 M&C residual period. These include the regular presence of coagulant in the 

drainage system; the presence of radioactive scale; the movement, maintenance, and repurposing 

of equipment; and presence of confined spaces within which maintenance work on subsurface 

drain pipes and utilities may have been conducted. Furthermore, to illustrate a distinction 

relevant to M&C, HHS found the following for Linde Ceramics (HHS, 2011, pp. 4–5): 

Specifically, some Board members noted that the decontamination activities were 

conducted with the knowledge that workers were exposed to a radiological 

environment. Consequently, radiological control measures appropriate for the 

time were likely utilized during decontamination activities. On the other hand, 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 38 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

renovation activities during the residual contamination period were conducted in 

what was expected to be a non-radiological environment, so no radiological 

control measures would be adopted. Additionally, worker accounts describe 

removal of heavy equipment and other activities during the renovation period that 

would be expected to reveal contaminated surfaces that would not have been 

decontaminated during the decontamination efforts at the end of the operational 

period. Therefore, the Board was not convinced that radiological data from the 

decontamination efforts during the operational period were sufficiently 

informative about exposures in the renovation period. Based upon this concern, 

the Board determined that such data could not be used in dose reconstructions for 

the renovation period. 

Finally, HHS concluded the following for Linde Ceramics (HHS, 2011, p. 5): 

There is insufficient support for NIOSH’s position that the decontamination 

activities at the end of the operational period were sufficiently similar to 

renovation activities during the renovation period. Because of the proposed 

differences between the two periods, NIOSH cannot be certain that the 

radiological data from the decontamination efforts during the operational period 

sufficiently account for exposures during the renovation period. Therefore, it is 

not feasible to reconstruct radiation doses with sufficient accuracy for the 

renovation period. 

A judgment on the question of whether there is sufficient similarity of conditions and processes 

between the D&D-era during which the 1995 characterization sample were completed and the 

preceding M&C residual period maintenance activities resides with the Board, as it did for Linde 

Ceramics. But it is clear that there are uncertainties related to source terms and exposure 

pathways for the M&C residual period that may not be addressed with sufficient accuracy by 

NIOSH’s current inside subsurface bounding model. 

7.2 Work Group concern: Worker protection

An August 16, 2023, M&C WG presentation stated that “maintenance workers were unaware of 

radioactive contamination and operated without radiological controls and health physics 

oversight” (ABRWH, 2023b, slide 7). 

7.2.1 NIOSH response: Worker protection

Work practices such as those specified in the WG’s concern do not affect the source term of any

of the “three legs of the stool” that form NIOSH’s bounding method because the M&C model 

does not assume any worker training or the use of engineering and administrative controls 

(NIOSH, 2023b, p. 31). 

7.2.2 SC&A response

As explained in section 7.1, citing the Linde Ceramics SEC precedent, this comment is directed 

at the overall uncertainties of comparing the processes and conditions of one time period to 

another at a site:
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 39 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

In order for radiological data from one time period to be considered informative 

about exposures during another time period, there should be some similarity of 

conditions and processes between the two periods. [HHS, 2011, p. 4] 

The distinct differences among how workers conducted their work, the conditions and processes 

of that work, and the radiological controls under which they performed their activities lead to 

greater uncertainty over a comparison between the D&D-era exposure potentials and those of the 

pre-1995 residual period. To paraphrase a key basis for the SEC designation for Linde Ceramics, 

the corollary question for M&C that the Board would address is whether the radiological data 

from the 1995 pre-decontamination surveys were “sufficiently informative” (HHS, 2011, p. 5) 

about exposures in the preceding 27 years of the residual period. 

7.3 Work Group concern: Claimant-favorable assumptions

An August 16, 2023, presentation states (ABRWH, 2023b): 

How does M&C compare with other AWEs?

 . . . 

• SC&A finds M&C to be comparable to facilities with more intrusive 

activities, e.g., those related to renovation as defined by NRC and found at 

Linde Ceramics (SEC class designee).

• Why is this important?

o Standard models from OTIB-0070 and TBD-6000 assume more passive 

worker activities related to occupancy, like other non-SEC AWEs. 

[slide 9] 

. . . 

• NIOSH use of “extreme conservatism” to account for M&C’s “intrusive 

activities, high exposure conditions, uncertain facility activities, or unknown 

contamination sources” (NIOSH, 2023a) results in a high bounding value – 

but is it plausible? [slide 12] 

7.3.1 NIOSH response: Claimant-favorable assumptions

The information presented at the August 16, 2023, Advisory Board meeting is 

inaccurate, especially regarding OTIB-0070. It could be argued that TBD-6000 

allows default assumptions which may be considered more passive, but OTIB0070 makes no such assumptions and requires the user to make a thoughtful 

selection. It is a document that provides options to select models that are as 

aggressive or passive as appropriate.

SC&A and the Work Group are misinterpreting NIOSH’s use of the phrase 

“extreme conservatism” to mean implausibly high. NIOSH is using conservative 

assumptions that are appropriate for a bounding scenario. The maximum 

predicted committed effective dose equivalent is still only 71 mrem which is not 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 40 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

implausibly high and is on par with normal background radiation levels every 

American experiences. [NIOSH, 2023b, p. 32] 

7.3.2 SC&A response

The context of the Board’s comment regarding OTIB-0070 and TBD-6000 is the application of 

these modeling guides in practice, specifically for M&C. As noted earlier, SC&A questions the 

application of such standard modeling approaches for the unique circumstances at M&C during 

the residual period, where more intrusive activities, or unique conditions or processes, make the 

“thoughtful selection” (NIOSH, 2023b, p. 32) of appropriate resuspension and dust loading 

factors important.

NIOSH itself noted that OTIB-0070 had not been adapted in the ER to adequately consider the 

more intrusive activities described by M&C workers:

During the first day of interviews, NIOSH interviewed [redacted for privacy] and 

a knowledgeable health physicist. The information indicated that the workers at 

M&C conducted more intrusive work into subsurface areas than previously 

considered in the ER. The ER models resuspension (OTIB-0070) and does not 

specifically address potential exposures from digging, snaking/replacing clogged 

drain lines, or repurposing M&C equipment (e.g., removing and replacing mill 

units). [NIOSH, 2017b, PDF p. 2] 

This subsequently led to NIOSH adding its six bounding models for such exposures. 

Similarly, SC&A expressed reservations in its 2021 review regarding the use of a generic dust 

loading value, 212 ug/m3

, from OTIB-0070 for outdoor and indoor excavations at various 

facilities and sites, noting that such assumptions should be uniquely evaluated at each site of 

proposed use (SC&A, 2021, p. 12). NIOSH agreed with SC&A that “one size will not fit all,” 

and indicated that it “will address this further during the next ORAUT-OTIB-0070 revision” 

(NIOSH, 2022, p. 5).

SC&A’s response to NIOSH’s response on the application of extreme conservatism in support of 

its exposure modeling is incorporated in section 8.1 of this paper. 

7.4 Work Group concern: AWE equipment

An August 16, 2023, Board meeting presentation states (ABRWH, 2023b, slide 10): 

What were typical intrusive activities and exposure pathways during M&C 

residual period?

. . . 

• Maintenance, movement, and replacement of repurposed AWE equipment 

7.4.1 NIOSH response: AWE equipment

NIOSH has previously responded to this concern. Texas Instruments reported to 

the NRC that the AWE operations (Buildings 3, 4, and 10) were decontaminated 

and decommissioned and that all radioactive materials were removed during the 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 41 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

period from 1955 to 1968; the largest Building 10 cleanup effort occurred at the 

end of 1958. “...contaminated noncombustible scrap material and machinery were 

collected in 55-gallon steel drums and disposed of through authorized agencies or 

buried on-site in compliance with 10CFR20.304” [Sowell 1985, PDF p. 12]. 

[NIOSH, 2023b, p. 32] 

7.4.2 SC&A response

NIOSH’s response does not address the potential exposure pathway posed to M&C maintenance 

workers from the repurposing, movement, and subsequent maintenance of AWE-era equipment 

during the residual period. As detailed by SC&A’s footnote 7 in the supplemental review 

(SC&A, 2022, p. 14, n. 7):

Routine maintenance on equipment is cited by former workers ([ORAUT, 2017e], 

p. 5; [ORAUT, 2017f], p. 3; [ORAUT, 2017g], p. 4), and was performed by the 

M&C Repair and Maintenance group. It was also identified by NIOSH as not 

being addressed by the ER resuspension models (OTIB-0070) and involved 

“repurposing M&C equipment (e.g., removing and replacing mill units)” 

([NIOSH, 2017b], p. 1). A former worker noted that relocating equipment in 

Building 10 was a regular activity that typically took place on weekends 

([ORAUT, 2017e], p. 12). The status of equipment carried over from the pre-1968 

AWE operational period is not addressed explicitly in the ER. It should be 

assumed that any equipment used in the operational period, prior to D&D, may 

have had internal contamination, as well as contamination under it, to which 

maintenance workers would have been later exposed when servicing [or 

repurposing] that equipment or moving it. This issue was raised during Board 

discussions about the Linde SEC by a Board member with firsthand experience, 

who found that when workers “were actually moving, removing production 

processes . . . we always found the most contamination was in the footprint of 

these processes” (ABRWH, 2011, pp. 267–268). For M&C, it is reported that 

compressed air was typically used to clean mechanical equipment (Elliott & 

Lorenzen, 2017), which could have resuspended internal contaminants. The 

concentration of this contamination may be higher than that of surface 

contamination surveys conducted in 1967–1968 and could have included uranium 

and thorium particulates.

While NIOSH further clarified that “a few substantial pieces of equipment were left in place with 

residual contamination in inaccessible locations” (NIOSH, 2023a, p. 7), SC&A (2023) responded 

further:

SC&A’s question, here, regards the repurposing of M&C equipment, which does 

not appear to be addressed in terms of covered exposure to M&C workers 

performing later maintenance on that equipment during the residual period. While 

the SEC-00236 ER does cite the contamination surveys performed and that a few 

substantial pieces of equipment were left in place with residual contamination in 

inaccessible locations, NIOSH does not address whether later repurposing of 

M&C equipment may have led to exposures to the workers performing the 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 42 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

repurposing and whether later maintenance on such equipment would have been a 

potential exposure pathway. [SC&A, 2023, p. 10] 

In its August 2023 response, NIOSH continues to contend that given the D&D activities and 

surveys conducted, “all radioactive materials were removed during the period from 1955 to 

1968,” and that contaminated equipment was disposed of as waste (NIOSH, 2023b, p. 33): 

NIOSH has previously responded to this concern. Texas Instruments reported to 

the NRC that the AWE operations (Buildings 3, 4, and 10) were decontaminated 

and decommissioned and that all radioactive materials were removed during the 

period from 1955 to 1968; the largest Building 10 cleanup effort occurred at the 

end of 1958. “...contaminated noncombustible scrap material and machinery were 

collected in 55-gallon steel drums and disposed of through authorized agencies or 

buried on-site in compliance with 10CFR20.304” [Sowell 1985, PDF p. 12]. 

However, such D&D activities would not have addressed residual contamination under and 

within AWE-era machinery and equipment that remained, which may have been later moved and 

repurposed by M&C workers. 

SC&A finds that a significant source of exposure to M&C maintenance workers may have been 

residual contamination under and within AWE-era machinery and equipment that was not 

decontaminated and decommissioned. The application of a bounding intake without 

consideration of such identified source terms and potential exposure pathways needs to be 

reviewed by the WG from the standpoint of completeness, sufficient accuracy, and plausibility. 

7.5 Work Group concern: Burial area

An August 16, 2023, presentation states (ABRWH, 2023b, slide 10): 

What were typical intrusive activities and exposure pathways during M&C 

residual period?

 . . . 

• Excavating contaminated soils, including those near or within radioactive 

waste burial sites

7.5.1 NIOSH response: Burial area

NIOSH developed a model to bound exposure during subsurface work in areas 

outside of Building 10 including the burial ground. However, during Work Group 

discussions NIOSH agreed to assign doses from the Building 10 subsurface model 

to all workers since workers constantly moved about the site and because those 

doses were more claimant favorable. In addition, at the July 13, 2023, M&C 

Work Group meeting, the Work Group conceded other exposures including those 

from the burial ground with the following statement: (NIOSH 2023b, pp. 33-34) 

Attention to subsurface exposures in Building 10. NOTE: The Work Group 

(WG) and staff generally agreed that the greatest exposures to the M&C 

maintenance workers came from the subsurface work in Building 10. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 43 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

Since the NIOSH bounding model is applied to all claimants, further 

discussion during this presentation focuses solely on such subsurface work 

and whether or not it is bounded. [ABRWH 2023a, PDF p. 8]

If the Work Group is aware of new technical information related to the burial 

ground, NIOSH requests a copy so we may consider it. 

[NIOSH, 2023b, pp. 32–33] 

7.5.2 SC&A response

The WG may want to add its considerations in response to this issue, but SC&A finds no 

concern, on its part, in the presentation material cited by NIOSH. The excavation of subsurface 

soil within the burial ground area represents an intrusive activity that may have had exposure 

potential to those workers conducting the excavation. However, the question of whether 

NIOSH’s bounding approach for such potential exposures using a blended source term has been 

addressed by SC&A and the WG based on NIOSH’s response paper and subsequent WG

discussions. SC&A has no new technical information to add related to the burial ground. 

7.6 Work Group concern: Confined spaces and applying Mound surrogate data

SC&A’s comment and NIOSH’s response have been addressed in section 5 of this paper, with a 

more specific treatment in section 5.4. 

8 Other Issues of Significance

In its supplemental review and followup responses, SC&A raised several additional issues 

relevant to sufficient accuracy and plausibility as they pertain to NIOSH’s proposed bounding 

models for M&C being reviewed by the WG. These were not addressed fully in NIOSH’s 

August 2023 response. 

These include NIOSH’s stated application of extreme conservatism in its bounding models and 

reference to assumed programmatic performance to substantiate the conservatism of the 95th 

percentile soil contamination value being used. Sections 8.1 and 8.2 summarize these two issues, 

respectively.

8.1 Application of extreme conservatism

NIOSH refers to the “extreme conservatism in its modeling to account for intrusive activities, 

high exposure conditions, uncertain facility activities, or unknown contamination sources” 

(NIOSH, 2023a, p. 17), but this NIOSH approach employs a maximized value to compensate for 

the lack of any source term and monitoring data for inside subsurface potential exposures for the 

entirety of the residual period up to 1995. SC&A addressed the plausibility of this approach in its 

Line of Inquiry 3 from its supplemental review:

Are the available source term, survey data, and other information applied by 

NIOSH to support its dose bounding methods sufficiently accurate and plausibly 

applied? [SC&A, 2022, p. 7] 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 44 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

SC&A’s assessment of this question can be found in its April 2023 response (SC&A, 2023, 

pp. 15–16): 

A guiding principle that NIOSH follows for addressing the “uncertainty around 

the work performed” or the “complete understanding of the work performed” is 

that it is “NOT an issue when the bounding doses are very low, and specifically, 

during AWE residual periods such as at M&C” (NIOSH, [2020b], slide 14). 

However, as pointed out by SC&A’s supplemental review, the question of 

determining a bounding dose in the absence of sampling data during the AWE 

residual period and applying sufficient conservatism to it is not without precedent 

and carries with it the question of plausibility. As pointed out during the Board’s 

Linde review, if “carried to an extreme, we could take any site . . . and we could 

come up with what we think is the highest possible exposure at that site that 

would occur, and that would be bounding, and apply that to everybody that ever 

worked at the site” (ABRWH, 2011, p. 129). However, the essential questions, as 

the former Board Chair put it, are “is that a plausible bound? And then, who are 

we trying to characterize?” (ABRWH, 2011, p. 129). 

NIOSH’s response, that it has “incorporated extreme conservatism in its modeling 

to account for intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources” (NIOSH, 2023a, p. 17) at M&C for 

the residual period, raises the very concern raised by Dr. Melius during the Linde 

AWE proceedings that contributed to the Board’s decision on that SEC 

evaluation. In the absence of source term and monitoring data for the facility time 

period in question, is it plausible to incorporate what NIOSH terms “extreme 

conservatism” in its bounding value for inside subsurface exposures based on 

information from a much later time frame (27 years), from a different operation 

(pre-D&D), and with different work conditions when attempting to address what 

NIOSH terms “intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources”? (NIOSH, [2023a], p. 17)? 

While NIOSH notes that M&C dose estimates are relatively low and it has “a 

more complete data set to characterize M&C and a better understanding of M&C 

maintenance work than we had with Linde” (NIOSH, [2023a], p. 24), it has not 

addressed the increased exposure potential posed by confined space atmospheres, 

nor does it similarly consider the implications of coagulant oil discharges and 

airborne contaminant scale releases to its exposure pathway analyses. NIOSH 

may claim that the extreme conservatism of its modeling would bound even these 

exposure pathways, but in the absence of validating information, such a claim 

may be considered by the work group to be unfounded and implausible.

In its August 2023 response to a WG concern, NIOSH responded on this issue (NIOSH, 2023b, 

p. 32): 

SC&A and the Work Group are misinterpreting NIOSH’s use of the phrase 

“extreme conservatism” to mean implausibly high. NIOSH is using conservative 

assumptions that are appropriate for a bounding scenario. The maximum 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 45 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

predicted committed effective dose equivalent is still only 71 mrem which is not 

implausibly high and is on par with normal background radiation levels every 

American experiences.

SC&A citation of NIOSH’s explanation for its use of extreme conservatism was literally taken 

from its response to a key SC&A’s question: “The sediment readings taken in 1995 from a 

Priority-1 pipe obviously had a high uranium concentration, but is it the bounding case for all 

inside subsurface activities for the previous 27 years of the residual period?” (SC&A, 2022, 

p. 23). 

NIOSH responded that it “is not back-applying conservative D&D measurements” (NIOSH, 

2023a, p. 16). Instead, “NIOSH is back-applying measurements taken by M&C and NRC 

Contractors before D&D that they used to characterize the area to determine the maintenance and 

subsequent D&D work controls,” and “in addition, NIOSH incorporated extreme conservatism in 

its modeling to account for intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources” (NIOSH, 2023a, pp. 16–17). 

Given the breadth and depth of unknowns and uncertainties imbedded in this bounding approach, 

it will be incumbent on the Board to gauge whether this represents a plausible means to define an 

upper bound for past exposures of M&C maintenance workers during the 27 years in question. 

Likewise, if NIOSH’s bounding model cannot account for M&C’s “intrusive activities, high 

exposure conditions, uncertain facility activities, or unknown contamination sources” (NIOSH, 

2023a, p. 17) without resorting to extreme conservatism, the question of sufficient accuracy 

becomes important.

8.2 Conservatism of 95th percentile soil contamination value

SC&A provided observation 2 in its supplemental review: “References to the M&C safety and 

health manual, NRC inspection results, operator training, and other programmatic considerations 

do not necessarily substantiate the conservatism of the 95th percentile soil contamination value 

being applied” (SC&A, 2022, p. 35).

NIOSH observed in an earlier response to WG comments that, “although comprehensive sample 

data used to characterize earlier periods did not become available until 1983–1995, NIOSH is 

aware of the safety program that was in place during the residual period” (NIOSH, 2020a, p. 17). 

NIOSH proceeded in that response and others to “make the case that M&C’s area monitoring 

assures that the 95th percentile soil-contamination value is conservative based on routine 

surveys of Building 10 during the first 14 years of the residual period (1968-1981)” (NIOSH, 

2021, pp. 7–8; emphasis added).

In response to SC&A’s observation 2, NIOSH noted that it “was not using the M&C Safety and 

Health manual, NRC inspection results, operator training, and other programmatic considerations 

to justify using the 95th percentile” (NIOSH, 2023a, p. 23; emphasis added).

In its April 2023 response, SC&A emphasized that “whether using these program documents to 

justify, or to demonstrate, corroborate, illustrate, or show that such monitoring procedures and 

oversight ‘assures’ that the 95th percentile soil contamination value is conservative is a 

distinction with little difference” (SC&A, 2023, p. 12). SC&A reaffirmed that it stands by its 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 46 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

observation that the program references NIOSH cites “do not necessarily substantiate the 

conservatism of the 95th percentile soil contamination value being applied” (SC&A, 2022, 

p. 37). 

9 Conclusion

In its presentation to the full Advisory Board on August 16, 2023, the M&C WG summarized its 

unresolved concerns for the M&C Petition 00236 evaluation (ABRWH, 2023b, slide 19):

• Intrusive work activities by maintenance workers at M&C during the residual 

period led to potential exposures for which there are no available monitoring 

data. 

• NIOSH applies 1995 D&D survey data as basis for an upper bound for 

residual period exposure. For radiological data from one time period to be 

considered informative about exposures during another time period, there 

should be sufficient similarity of conditions and processes between the two 

periods. 

• Although NIOSH has proposed a claimant-favorable “inside subsurface” 

bounding concentration (6,887 pCi/g), there remains uncertainty about source 

terms and exposure pathways during the residual period [prior to pre-D&D 

characterization], 1968–1997.[9]

9 The residual period prior to pre-D&D characterization, as noted, is actually 1968–1995. 

• There is insufficient information available to account for the exposure 

contribution of confined spaces, pipe scale releases, and released coagulants in 

a workplace not controlled as a radiation environment, unlike that of the later 

D&D era at M&C from which NIOSH draws its data.

• The application of “extreme conservatism” in formulating the proposed upper 

bound concentration to account for “intrusive activities, high exposure 

conditions, uncertain facility activities, or unknown contamination sources” 

may not be a plausible approach to compensate for inadequate or insufficient 

information. 

The WG’s proposed conclusion is (ABRWH, 2023c, slide 15): 

Because of the identified differences between the two periods (residual vs. D&D 

era), there is insufficient basis to conclude that radiological data from D&D 

efforts (including pre-D&D surveys) are sufficiently informative about exposures 

arising during the entirety of the M&C residual period to be applied in the manner 

proposed by NIOSH. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 47 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

SC&A’s review of NIOSH’s August 22, 2023, response paper did not identify information or 

analyses that materially affect the WG’s concerns and proposed conclusion. 

SC&A concludes NIOSH has a path forward to address the confined space issue: (1) it is 

acknowledged as a TBD issue, and (2) SC&A’s supplemental review identified options for 

revised resuspension factors (and accordingly a derived dust loading factor). However, 

uncertainties remain for source terms related to in-pipe contaminated sediments (due to the 

presence of coagulants) and in-pipe interior surface contamination (scale) during the pre-1995 

M&C residual period. These source terms are not accounted for in the proposed inside 

subsurface bounding model, and application of the compensatory “extreme conservatism” 

measures defined by NIOSH may not be considered sufficiently accurate and plausible by the 

Board. These source term uncertainties are compounded by likely disparities in the exposure 

potential between M&C maintenance workers and D&D workers, undetermined worker 

exposure due to repurposing and maintenance of AWE-era machinery and equipment, and the 

acknowledged intrusiveness of M&C maintenance worker activities compared with other AWEs. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 48 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

10 References 

Advisory Board on Radiation and Worker Health. (2011). 75th meeting Thursday, February 24, 

2011 [Transcript]. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2011/tr022411.pdf

Advisory Board on Radiation and Worker Health, Metals and Controls Work Group. (2023a, 

July 13). Statement by David Kotelchuck, Work Group member [PowerPoint slides]. 

Teleconference meeting of the Advisory Board on Radiation and Worker Health, Metals & 

Controls Work Group. SRDB Ref. ID 197979 

Advisory Board on Radiation and Worker Health, Metals and Controls Work Group. (2023b, 

August 16). Update: M&C Work Group review of SEC-related issues [PowerPoint slides]. 153rd 

Meeting of the Advisory Board on Radiation and Worker Health, Augusta, GA. 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/pres/2023/bd-metcontsec236issues-081623-508.pdf

Advisory Board on Radiation and Worker Health, Metals and Controls Work Group. (2023c, 

July 13). M&C Work Group review of SEC-related issues [PowerPoint slides]. Teleconference 

meeting of the Advisory Board on Radiation and Worker Health, Metals & Controls Work 

Group. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/pres/2023/bd-metcontsec236supprev071323-508.pdf

Alazaiza, M. Y. D., Albahnasawi, A., Ali, G. A. M., Bashir, M. J. K., Nassani, D. E., Al 

Maskari, T., Abu Amr, S. S., & Abujazar, M. S. S. (2022). Application of natural coagulants for 

pharmaceutical removal from water and wastewater: A review. Water, 14(2), 140. 

https://doi.org/10.3390/w14020140

American Water Works Association. (2011). Operational control of coagulation and filtration 

processes (AWWA Manual M37, 3rd ed.). AWWA. 

Argonne National Laboratory. (2003). User’s manual for RESRAD-BUILD version 3

(ANL/EAD/03-1). https://web.evs.anl.gov/resrad/documents/ANL-EAD-03-1.pdf

Campbell, B. (2022, March 8). What is coagulation for water treatment? What is coagulation, 

how does it work and what types of coagulants exist? Wastewater Digest. 

https://www.wwdmag.com/what-is-articles/article/10940184/what-is-coagulation-for-watertreatment 

Centers for Disease Control and Prevention. (2022, May 16). Water treatment. 

https://www.cdc.gov/healthywater/drinking/public/water_treatment.html

Chase, K. (2019, July 1). Confined spaces: Airborne dust & particulates accumulate quickly. 

Industrial Safety and Hygiene News. https://www.ishn.com/articles/111046-confined-spacesairborne-dust-particulates-accumulate-quickly

Elliott, M. J., & Lorenzen, W. A. (2017, August 18). Special Exposure Cohort Petition 

SEC00236, Metals & Controls (TI/M&C) Attleboro Site, written statement for August 24, 2017 

Advisory Board meeting. SRDB Ref. ID 176446, PDF pp. 9–12. 
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 49 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

International Atomic Energy Agency. (2005). Radiological aspects of non-fixed contamination of 

packages and conveyances: Final report of a coordinated research project 2001–2002 (IAEATECDOC-1449). https://www-pub.iaea.org/MTCD/Publications/PDF/TE_1449_web.pdf

Minnesota Rural Water Association. (2020). Coagulation and flocculation. In Minnesota water 

works operations manual (5th ed). 

https://www.mrwa.com/WaterWorksMnl/Chapter%2012%20Coagulation.pdf 

National Institute for Occupational Safety and Health. (2011). Site profiles of Atomic Weapons 

Employers that worked uranium metals (Battelle-TBD-6000, rev. 1). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/bat-6000-r1.pdf

National Institute for Occupational Safety and Health. (2017a). SEC petition evaluation report: 

Petition SEC-00236, Metals and Controls Corp. (rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/sec/metcont/metconter-236.pdf

National Institute for Occupational Safety and Health. (2017b). NIOSH notes October 24 – 26, 

2017: Interviews for Metals and Controls [DCAS external memorandum to Metals and Controls 

SEC Working Group]. SRDB Ref. ID 192920 

National Institute for Occupational Safety and Health. (2018). Metals and Controls Corp. 

maintenance worker exposure model [White paper]. 

https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-metcontmaintwem-102418-508.pdf

National Institute for Occupational Safety and Health. (2020a). Response to Metals and Controls 

Corp. Working Group comments [Response paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/182169_red-508.pdf

National Institute for Occupational Safety and Health. (2020b, September 2). SEC-00236 Metals 

and Controls Corp.: NIOSH response to working group comments [PowerPoint slides]. 

Teleconference meeting of the Metals and Controls Working Group. 

https://ftp.cdc.gov/pub/FOIAREQ/182969-508.pdf

National Institute for Occupational Safety and Health. (2020c). Documented communication with 

Tim Taulbee on air monitoring and dust loading at the Mound Plant on October 15, 2020, and 

May 20, 2021. SRDB Ref. ID 183893 

National Institute for Occupational Safety and Health. (2021, January 21). Response to comments 

from the Metals and Controls Corp. Work Group meeting held on September 2, 2020 [Response 

paper]. https://ftp.cdc.gov/pub/FOIAREQ/184642_red-508.pdf

National Institute for Occupational Safety and Health. (2022, January 12). NIOSH response to 

SC&A’s Metals and Control Corp. Exposure pathway evaluation and dust loading commentary

[Response paper]. SRDB Ref. ID 191642 

National Institute for Occupational Safety and Health. (2023a, January 13). NIOSH response to 

SC&A’s supplemental review of M&C Work Group issues [Response paper].

https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-sca-mcwgissues-508.pdf
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 50 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

National Institute for Occupational Safety and Health. (2023b, August 22). NIOSH response to 

“SC&A review [April 2023] of NIOSH response [January 2023] to SC&A’s supplemental review

of M&C Work Group issues [August 2022]” [Response paper]. 

https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-metcontwgissues-082223-508.pdf

Oak Ridge Associated Universities Team. (2012). Dose reconstruction during residual 

radioactivity periods at Atomic Weapons Employer facilities (ORAUT-OTIB-0070, rev. 01). 

https://www.cdc.gov/niosh/ocas/pdfs/tibs/or-t70-r1.pdf

Oak Ridge Associated Universities Team. (2017a). Documented communication SEC-00236 

with [Former Worker #2] on Metals and Controls Corp October 24, 2017. SRDB Ref. ID 170018 

Oak Ridge Associated Universities Team. (2017b). Documented communication SEC-00236 

with [Former Worker #5] on Metals and Controls Corp October 24, 2017. SRDB Ref. ID 169916 

Oak Ridge Associated Universities Team. (2017c). Documented communication SEC-00236 

with [Former Worker #7] on Metals and Controls Corp October 25, 2017. SRDB Ref. ID 169938 

Oak Ridge Associated Universities Team. (2017d). Documented communication SEC-00236 

with [Former Worker #9] on Metals and Controls Corp October 25, 2017. SRDB Ref. ID 169924 

Oak Ridge Associated Universities Team. (2017e). Documented communication SEC-00236 

with [Former Worker #10] on Metals and Controls Corp October 26, 2017. SRDB Ref. 

ID 169919 

Oak Ridge Associated Universities Team. (2017f). Documented communication SEC-00236 

with [Former Worker #1] on Metals and Controls Corp October 24, 2017. SRDB Ref. ID 169918 

Oak Ridge Associated Universities Team. (2017g). Documented communication SEC-00236 

with [Former Worker #8] on Metals and Controls Corp October 25, 2017. SRDB Ref. ID 169923 

Oak Ridge Associated Universities Team. (2017h). Documented communication SEC-00236 

with [Former Worker #3, joined by Former Worker #4] on Metals and Controls Corp October 

24, 2017. SRDB Ref. ID 169925 

Occupational Safety and Health Administration. (2015). Confined spaces in construction: Pits

(DOC FS-3788). https://www.osha.gov/sites/default/files/publications/OSHA3788.pdf

Safe Drinking Water Foundation. (n.d.). Conventional water treatment: Coagulation and 

treatment. https://www.safewater.org/fact-sheets-1/2017/1/23/conventional-water-treatment

Saleem, M., & Bachmann, R. T. (2019). A contemporary review on plant-based coagulants for 

applications in water treatment. Journal of Industrial and Engineering Chemistry, 72, 281–297. 

https://www.sciencedirect.com/science/article/abs/pii/S1226086X18314965?via%3Dihub

SC&A, Inc. (2021, October 25). SC&A commentary on NIOSH’s approach to quantifying 

outdoor and indoor airborne dust loadings (SCA-TR-2021-SEC005, rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-airdustloadings-r0-508.pdf
Effective date: 11/22/2023 Revision No. 0 PC-1 (Draft) Response Paper Page 51 of 51

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

SC&A, Inc. (2022, August 22). Supplemental review of M&C Work Group issues (SCA-TR2022-SEC002, rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-metcontwgissues508.pdf

SC&A, Inc. (2023, April 25). SC&A review of NIOSH response to SC&A’s supplemental review

of M&C Work Group issues [Response paper].

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-reviewmetcontwgissues-508.pdf

Sowell, L. L. (1985). Radiological survey of the Texas Instruments site Attleboro, 

Massachusetts: Final report. SRDB Ref. ID 94371 PDF pp. 6–123. 

Texas Instruments, Inc. (1979). Environmental information report for 1979 HFIR facility license 

renewal by NRC. SRDB Ref. ID 13633 

U.S. Department of Energy. (1996). Hazard assessment for the General Motors site, Adrian, 

Michigan (DOE/OR/21950-1017). SRDB Ref. ID 14422 

U.S. Department of Health and Human Services. (2011, April 21). HHS designation of 

additional members of the Special Exposure Cohort under the Energy Employees Occupational 

Illness Compensation Program Act of 2000. 

https://www.cdc.gov/niosh/ocas/pdfs/sec/linde/lindehhsdes-107.pdf

U.S. Nuclear Regulatory Commission. (1999). Residual radioactive contamination from 

decommissioning: Parameter analysis [Draft report for comment] (NUREG/CR-5512, Vol. 3). 

https://www.nrc.gov/docs/ML0824/ML082460902.pdf

Vijayaraghavan, G., Sivakumar, T., & Vimal Kumar, A. (2011). Application of plant based 

coagulants for waste water treatment. International Journal of Advanced Engineering Research 

and Studies, 1(1), 88–92.

https://www.technicaljournalsonline.com/ijaers/VOL%20I/IJAERS%20VOL%20I%20ISSUE%2

0I%20%20OCTBER%20DECEMBER%202011/18%20IJAERS.pdf

Weston [Roy F. Weston, Inc.]. (1995). Sampling and analysis plan for the development of 

decontamination profiles – interior building areas, Texas Instruments Attleboro Facility. SRDB 

Ref. ID 197836 

Weston [Roy F. Weston, Inc.]. (1996a). Remediation of building interiors 4, 5, and 10 (SNM23/70-33, ver. 1.0). SRDB Ref. ID 114246, PDF pp. 5–201. 

Weston [Roy F. Weston, Inc.]. (1996b). Texas Instruments Incorporated Attleboro Facility: 

Building interiors remediation drainage system characterization. SRDB Ref. ID 165965, PDF 

pp. 6–31. 

Weston [Roy F. Weston, Inc.]. (1997a). SNM license termination hypothetical radiological dose 

and exposure rate assessment priority 2 drain lines (SNM-23/70-33). SRDB Ref. ID 197835 

Weston [Roy F. Weston, Inc.]. (1997b). SNM license termination radiological dose assessment

(SNM-23/70-33). SRDB Ref. ID 197838